Status "Unlicensed Product" on Windows 7

Status "Unlicensed Product" is shown in Microsoft 365 Apps on a PC with Windows 7.
The issue started yesterday.
Error message when trying to log on with business account: "Unfortunately, we cannot connect to your account. Please try again later."
The issue exists only on this PC.

I did the following actions:
Removed the stored credentials in the Credential Manager in Control Panel.
Removed the old product keys on the PC through CMD.
Removed the cached identities in HKCU registry at HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Common\Identity\Identities.
Enabled and disabled the modern authentication through the registry key "EnableADAL".