Another Sage problem.
The same old crap – program disappears after the splash screen, or after entering your password. In this case it was after entering password.
Only this time, the cause, or at least the fix, was different. After an hour of pissing-about re-installing, rebooting, deleting everything I could find related to Sage, re-installing again, etc., I remembered the dot-net trick, gave it a go, and whaddaya know, it worked.
The fix, is to go into Windows’ Programs and Features, then Turn Windows features on or off, and turn off .NET Framework 3.5, and also 4.8. Let that take effect, reboot, then turn them back on.
Jobs a goodun.
Do yourself a favour and move to Xero.