Windows 10 home fully up to date, 32 gig of ram 6 cores

Wasn't sure where to post this problem as it could be caused by a number of things?

Anyway, I use a dual monitor display connected to a Nvidia Geforce GTX 1650 super graphics card, the card is only 2 months old and has worked perfectly until I started my PC desktop yesterday morning. The PC booted up as normal, but only monitor 2 showed the main desktop, the other monitor would not switch on, yet I could move the mouse cursor onto that monitor even though all I could see on that monitor was a black screen.
This is where the fun starts:- I fiddled around with the hdmi cables, even trying a new one with no luck, then about an hour later the missing display suddenly came on again and continued working properly for the rest of the day?
Then today I started my PC and the monitor that didn't work yesterday was now working, but the monitor that was working yesterday was now a black screen?
So I know it is not the monitors that are at fault, and in Display Settings both monitors are shown and said to be working correctly? I have restarted the PC several times with no change, only one monitor displays.

I really don't know where to start trouble shooting this problem, I've checked the drivers and run the trouble shooter in Display Settings with no change?

Any advice and help welcomed?

- - - Updated - - -

Just swapped the power supply cables around and both monitors are now working? Don't know why this should affect either monitor, but it has!
Will wait until tomorrow before I start up again to see if they are both still working. Will let you know the outcome then.