FL.
I have done a fresh reinstall of FL 20 (uninstalled it completely and installed it with all defaults), and have made sure that my keyboard and language settings are set to US qwerty. When I have the on-screen ...
fine. I am not aware of any other software that is running that is taking over the right ALT key function but let me know if there's any usual suspects to look at.
FLStudio 20.5.1 [build 1193]
Windows 10 ...