Update from Mojave to Catalina
I'm trying to update my iMac from Mojave 10.14.6 to10.15.7 Catalina on my late 2013 model iMac but I am constantly receiving the error message "The requested version of macOS is not available."
When I try to update through a dmg file I receive the error "This update requires macOS version 10.15." and I cannot find that update anywhere.