Today I set up a new monitor on my SSD driven 3B+. After fighting the built in overscan on the monitor, and setting the resolution to perfection, I decided to do an update & upgrade. I noted a reminder to do a reboot to replace a running file. I can't remember which one it was, but it was near the end of the upgrade process.
When the upgrade had finished, I did the reboot. Now the monitor reports no signal. I know that the Pi is running, because this is a NAS and I can see and access the shared drive over my network. Unfortunately this is the only part of the NAS that is shared, and I can't seem to be able to use Putty to ssh in. I have the IP address of the Pi (at least the shared drive's IP), but the connection times out.
Any help to undo the changes that the upgrade made? Do I treat this as if no video was displayed on initial startup? Fighting my way into the case and SSD was not on my scheduled list of things to do today.