SUMMARY
I have two monitors. My graphic card is Nvidia. My main (default, HDMI) monitor is at right side, the secondary (DVI) one is at left and rotated 90 degrees clockwise. The same config is shared thru "Screen" Plasma dialog and in Nvidia configuration (as it should be).
Each time I reboot and Plasma begin to load, all widgets and panels of second monitor appears in the first one and viceversa. After some seconds (finishing loading desktop), all widget and panels are showed correctly in first monitor, but second is black. I can move mouse over it, but no click reaction or dialogs (for example, clicking on it and press <Alt><F2>). I need go to "Screen" Plasma dialog, make any change (for example, rotate 90 anticlockwise), apply changes (then second monitor shows content) and then again configure to 90 clockwise and accept (to let it as it should be).

STEPS TO REPRODUCE
1. Configure second monitor rotated 90º and apply
2. Reboot system

OBSERVED RESULT
Second monitor doesn't show nothing, but mouse pointer.

EXPECTED RESULT
To recover last configuration on each reboot.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: 
KDE Plasma Version: 5.20.2
KDE Frameworks Version: 5.75.0
Qt Version: 5.15.1

ADDITIONAL INFORMATION