The Windows Server update with the number KB5020282 introduces a feature that locks the administrator account after 10 unsuccessful password attempts within 10 minutes.
Since Hetzner uses static IP addresses, such brute-force attacks are not uncommon and may lead to the locking of your administrator account. You can modify the settings of this feature or completely disable it in the Local Security Policy. This option can be found in the Server Manager by clicking on «Tools» and then «Local Security Policy».
If your account has already been locked, you can whitelist your connection address in the firewall. You can find out about it here.
After activation and setting up the firewall, you will need to wait for at least 10 minutes for the rules to be applied. Upon logging in, please adjust the settings as indicated above.