TODAY, MARCH 29TH - SOLUTION - (It worked in my case) . I managed to make it work offline, but the other apps stopped working. When I turned on the PC today, the “Activation Manager” icon simply disappeared. I tried to install it again and error 1612 appeared, I tried to uninstall it and the same error appeared.
I used the app “MicrosoftProgram_Install_and_Uninstall.meta” to uninstall Steinberg Activation Manager and installed it again and it worked again. PC XPS DELL Windows 11.