My new MacBook Pro suddenly stopped recognizing external monitor (Dell U2515H) after 2 days of normal usage.
Yesterday, after I was done with my work, I closed the lid as usual and today, I opened the MacBook and the external monitor didn’t get detected.
The monitor is connected via USB-C -> HDMI cable (cost about 20$).
I have already tried restarting my mac, reconnecting the monitor and detect monitors in system preferences.
I have also tried reseting SMC and NVRAM. Unfortunately none of it worked.
Any help is highly appreciated as I really need my external monitor for work.
Fix for me:
Answered by Jim Vitek on December 27, 2020
I recently experienced the same issue: a new work-issued 16-inch Macbook Pro stopped recognizing a Dell monitor connected using an HDMI cable and a multiport USB C adapter.
I confirmed that the monitor and HDMI cable were fine by connecting them to another computer, tried two different multiport adapters (this one from StarTech and this one from Anker) in all four Thunderbolt ports (notably, all the non-HDMI ports on these adapters have consistently functioned without issue), reset the NVRAM (as suggested in Apple's troubleshooting instructions for external displays), and tried power cycling the monitor as suggested in the top answer.
The only thing that worked for me was:
Since the first time I stumbled on this solution, the MacBook has repeatedly failed to detect the external monitor (usually a few days after the issue last occurred) and these steps have resolved the problem every time.
On a cantankerous note, I feel obliged to note that the prevalence of this issue (assuming a google search is representative) is disappointing given the expense and corresponding implication of quality of Apple hardware.
Answered by Reign of Error on December 27, 2020
Tired of constant reboots that always help, resetting SMC, plugging/unplugging cables, the faster solution turned out to be:
Answered by MrA on December 27, 2020
Ridiculously the solution for me, which I discovered purely out of frustration, was to use short, sharp taps (2x) on the F2 as opposed to a slow single tap which had worked previously. Now that works every time. I know it sounds ridiculous but this issue was doing my head in and that is was I accidentally discovered! very low tech solution!!
Answered by ness spiller on December 27, 2020
Late entry here but it might be useful to someone so here we go.
If your computer has been working with an external monitor but suddenly stopped supplying an image feed
Problem & Tinkering
I have a late 2016 MBP 15 running Catalina 10.15.4 connected ta an Eizo CG248 via a displayport - USB C connection. It has worked without issues for over a year. Then at one point I closed my mac and turned of the screen, opening the mac up again the screen is not recognized at all. Screen is blank and turns it self off after signaling "no input found".
As I used to work in a store selling apple computers I tried all the regular tricks. Rebooting everything connecting, disconnecting, trying to force find the screen. Resetting SMC and p-ram to no avail. I did have a hyperdrive, laying around with a HDMI out. Connected it and got an image but only with 30hz refreshrate that I wasn't able to change, so it wasn't a viable option, as I need 60. The hyperdeck specs said it would provide 60hz via usb out but for some reason it did not and the HDMI cord was a 2.0 one. Tried again with 2 different display to usb c cords. And bought a mini displayport to displayport. Through the hyperdeck also got a 30hz refresh rate. Other computers in the household connected to the screen fine. But not my work computer and it was really annoying.
I realized that there was one option I hadn't tried, if it was the hyperdeck that was resticting the HDMI i could try a HDMI - usb c cord capable of 60hz. So I got one and. I got an image.... At 30hz.
I thought I'd try again to connect the displayport - usbc and.... It worked. What?! All the glory in resolution and refreshrate was back. And it has been working since! So it seems that my computer for some reason had a hangup that was cured by connecting another type of cord, but in my case not through a hyper deck. I then returned the cables I bought since I didn't need them and now I'm back to status quo with my original hardware.
Go buy all the cord variations you can connect between your monitor and computer. Try them out one by one and retry your original connection in between. Then simply return the cords you don't need to the store again. If it works it works as It did for me. And it's free to try.
Hope you all get your image back!
Answered by Tomas Pettersson on December 27, 2020
The same malaise hit my external monitor today. The only crime I did was to unplug the Mac from the dock and plug it back into the dock later. No display --after weeks of this sequence followed successfully, and new gear (one month old display, cable, docking station).
I spent HOURS today trying every combination of troubleshooting under the sun. The basic troubleshooting strategies applied were:
The aggregate of the successful answers here suggested this was a power sequencing issue. I finally tried powering off the power strip and powering everything back on at once. Viola! Display popped up immediately. At this point I was in the simplest configuration: display connected directly to laptop and no docking station.
Given all my troubleshooting I believe the culprit was the Mac itself. The display and cable were working, it was the Mac that got into a state where it could not see external Thunderbolt devices.
Sadly I just checked the Mac System Report and Thunderbolt still reports no devices connected to its bus ports. But in the middle of everything it did see the docking station. So it's not the panacea I had hoped as I can see some things correctly but not others of significance.
CalDigit docking station after all the troubleshooting just died. The blue LED doesn't light. The Digital Optical port on the back which is lighted is no longer. Either the transformer gave up the ghost, or the dock itself fried from all the connecting and reconnecting. I love the product design and features, but I have one at work, and it's been flakey on occasion (refusing to power up like now).
Answered by Bill Gale on December 27, 2020
Similar issue with Philips monitor, MacBook Pro 2017 TB, and Digitus USBC-DP dongle. My solution:
Answered by felice on December 27, 2020
I had this issue for HOURS and was going crazy. Ended up the fix (for me at least) was downloading the latest video driver for Dell (my monitor is Dell), and that fixed it. So have a look and see if you can download any drivers :-)
Answered by Elise Roberts on December 27, 2020
Had a similar problem MacBook Pro 2018, Belkin dock and USB-C HP monitor.
Now it is working again.
Answered by waseq on December 27, 2020
I had same problem. Spent an hour with Apple tech support, we finally figured out I needed a USB-C to miniDisplay port dongle, not the USB-C to Thunderbolt 2 dongle I purchased with the new MacBook Pro. (Outward appearance of the miniDisplay port and the Thunderbolt 2 port are the same.) Once I had the right dongle, the monitor worked immediately.
Answered by David Cook on December 27, 2020
I had the same issue with Macbook Pro w/touchbar, but with 2x Dell u2415Q (both stopped working at the same time). They are connected via 2x Kanex USB-C to DisplayPort female dongles; then using standard DisplayPort cables from there.
After much faffing around, the solution ended up being to simply disconnect the dongles, from the cables, and reconnecting at the dongle level. I had tried disconnect from Macbook, and disconnecting from the screens, but didn't try disconnecting the middle connection (separating the dongles from the cables and back again).
All up and running again. Hope it helps someone!
Answered by JeremyTM on December 27, 2020
This might seem silly but this worked for me (also better to exhaust all options):
I use a dock connected into the thunderbolt port. My charger connects into the dock and so does the monitor (dp to mdp cable). My Dell U2715H suddenly stopped working too. I tried a bunch of different things but nothing worked. I decided to take my laptop to a service center. I just happened to remove my charger from the dock first (with the monitor still connected) and suddenly the desktop showed up on my monitor and every thing was working fine. I just connected my charger back and everything was back to normal.
Answered by iammrmehul on December 27, 2020
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