Not able to login to sandbox

When you add IP restrictions to a profile, you can only log in from the addresses whitelisted in that profile. Access from any other IP will be denied.

I assume there are other administrators using your system. That is the only way that someone other than yourself could have added restricted IP ranges.

Salesforce will not allow you to lock yourself out of an org, so if you add IP restrictions, you have to add the IP address you're connecting from. This means that whoever set up the restrictions, he must have added his own IP to the list.

I would contact the other administrator(s) and ask why the IP ranges were added and if necessary, ask the to add your own IP or remove IP restrictions altogether.

Or, if you have another sysadmin profile, I would try to use with a user belonging to that other profile. Maybe that profile has different (or no) IP login restrictions.