On my laptop running Windows 10 Pro 22H2 Rainlendar Pro 2.19 won’t install properly unless the C:\Programs\Rainlendar2 plugins folder is deleted manually. Normally updating Rainlendar just involves rewriting what is already there but when I tried to update to the latest version I got multiple errors, which I ignore, and when I executed the program an error message about plugins needing to be removed. If you delete the Rainlendar folder (C:\Programs\Rainlendar2) or the plugins folder before installing everything works.
Don’t ignore the errors in the installer. It will break the application. The errors are shown if Rainlendar is already running when you try to upgrade so you need to manually close it and then run the installer.