My first suggestion is to check that the monitors’ hardware are fine - cables and power supplies work fine?
Can you use terminal (ctrl+alt+t) and grep " install " /var/log/dpkg.log to see what you installed recently? You’d have to shortlist based on when the monitors were last functioning.
My wife’s PC runs Core and her dual monitors are functioning fine, so I can’t help by checking my own.
And was running super until the changes in the Display prompt. In the prompt it doesn’t even give the option of multiple screens anymore. No clue where to find the new one.
Ok, and can you check if you are using Nouveau or Nvidia drivers- or Proprietary graphics drivers?
You can go to Software & Updates and go to the Additional Drivers tab and check for available drivers there, as well. But I suspect you may need to roll a driver back, rather than update one.
Sorry, I slipped into lingo, there.
If you could open a terminal by hitting the ctrl+alt+t keys on your keyboard.
Paste into it:
uname -a
This will print an output of that command, in this case, the command asks for system information. The information is what version kernel you are running. The Linux kernel is similar to how Windows uses the NT kernel and Android uses the... Android kernel (Which is a modified Linux kernel).
The kernel is what delegates functions to the processor. You might consider it like a Conductor.
When you run the above in terminal, you can highlight the output with your mouse, then right click and choose "copy" and then paste that here in this thread.