I've been trying to upgrade from Mojave to Catalina or big sur on my iMac. and get message "The requested version of macOS is not available." I can't run some of my most important apps (esp. PSE organizer) on Montery. Any suggestions?
iMac 21.5″, macOS 10.14
usually when you get "The requested version of macOS is not available." that means that the Mac is not compatible with a given macOS.
you can check these links to see if the Mac is compatible or not with Catalina, Big Sur.
macOS Catalina 10.15 hardware requirements
macOS Big Sur 11 hardware requirements
if the Mac is compatible, but you are still having difficulties, you can try and start the Mac into safe mode and try and apply the upgrade while in safe mode.
Start up your Mac in safe mode.
usually when you get "The requested version of macOS is not available." that means that the Mac is not compatible with a given macOS.
you can check these links to see if the Mac is compatible or not with Catalina, Big Sur.
macOS Catalina 10.15 hardware requirements
macOS Big Sur 11 hardware requirements
if the Mac is compatible, but you are still having difficulties, you can try and start the Mac into safe mode and try and apply the upgrade while in safe mode.
Start up your Mac in safe mode.
and if it is compatible with Catalina or Big Sur, you can find the downloads here: How to get old versions of macOS - Apple Support. please use safari as other browsers usually won't work.
upgrade to big sur or Catalina
