Marlin won't start up on modified CR10s

I have been adding a Hemera and BLTouch to my CR10s, and finally finished everything, flashed the firmware, and everything worked fine. However, I forgot about one thing (Probe_to_Nozzle_Offset), so I went back in made the changes, compiled it and that completed successfully. I uploaded it via Cura, and it gave me the upload finished message, so I closed Cura and went back to working. However, when I turned the printer off and back on, it wouldn’t boot up. It would only show the Marlin screen, see e.g. this video.

It stays like that for as long as I have looked at it.

Now I am also having troubles uploading new firmware. Cura will not detect the printer is connected, Arduino will not either, and Platformio gives me some timeout error, which I looked up and it means that the uploader couldn’t connect to the bootloader. I don’t know any other way to upload the new firmware, and for now my project is stuck because of it. I have 2 ideas of what happened:

1. The upload was not completed and was therefore corrupted when I closed Cura.
2. The build was broken, but because it compiled fine I don’t know how this could be.

Does anyone know what could have happened, or how to fix it?

EDIT:

VS code/platform.io recognized the usb port, and tried sending over the firmware.hexfile, but all I got was this warning over and over:

avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_getsync(): timeout communicating with programmer

And then later:

avrdude: stk500v2_command(): failed miserably to execute command 0x10
avrdude: initialization failed, rc=-1
         Double check connections and try again, or use -F to override
         this check.

Everything was plugged in, and the lights on the board were being powered by the computer, so there was still a connection, but for some reason this warning happened, and then went right back to the avrdude: stk500v2_ReceiveMessage(): timeout

Also, I looked in the device manager when my USB to ISP was connected, and it wouldn’t show, which explains why Arduino IDE won’t upload the bootloader, but in that case is my only option to buy an Ardunio?