I have Raspbian 9.9 installed on the SD card which runs fine and displays to my monitor via DVI to HDMI adapter.
I formatted a 1TB SSD to ext4 and followed the https://pimylifeup.com/raspberry-pi-boot-from-usb/ tutorial.
After successfully running from that drive for several weeks without the SD card, I added Nextcloud server which has been up for a month with 300gb of data.
Today, after updating and upgrading (sudo apt-get update && sudo apt-get upgrade), my monitor would not display after reboot.
If I return to the SD card and boot, the monitor works normally (as it does with several other machines). I can connect to the Nextcloud server from a client at 10.0.1.4/nextcloud on my home network.
Another working monitor behaves the same way. When I try to ssh the Pi, it does not accept my password.
Is there anything else to check before wiping the Pi, reformatting the SSD to EXT4, and beginning again? The Pi is powered, and the SSD is also.
The SSD mounts as an external drive when I boot from the SD card.