Why would my desktop suddenly stop recognizing my second monitor and how do I fix it?

[Replicant]

Why would my desktop suddenly stop recognizing my second monitor and how do I fix it?

When I start my computer, the BIOS message appears on one monitor in my dual monitor set up.
But when the computer login message appears on my windows operating system, it appears only
on the other monitor, and the desktop does not spread to both monitors.
Rebooting used to solve this problem last week, but now even that fails.
Please help.

-System Information-
OS: Windows 10 (Build 18362.1316)
CPU: x64
File System: NTFS

 

[root]

Hi, welcome to Computer Forums

Apologies that your post didn’t go live immediately; the spam filter can be a bit overzealous at times.

This is a bit of a strange error for sure.
For a quick fix, are you able to try holding the Windows Logo key + P on the keyboard?

This should bring up a list of options - try both duplicate and extend, do either of these work?

Does the system detect the second monitor at all i.e in display properties?