2nd monitor doesn't stay rotated on Macbook Air 2012 (Catalina)

Macbook Air 2012 running Catalina.

2nd monitor plugged into thunderbolt port. Monitor stays rotated at 90 degrees. Every time I reboot the computer, or wake it up from sleep, the 2nd monitor goes back to landscape mode and has to be re-rotated via the system preferences display menu.

How do you make the rotation settings for the 2nd monitor more permanent?