Hello again,
Tried the routine suggestion. Didn't work....Didn't do anything.
Last night Samsung released an OneUI update and bang PhoneLink fails to show the lockscreen on my PC!.....AGAIN!
Uninstalling the app to the factory version no longer worked. Neither does updating Phone Link from the Samsung store.
Does Phone Link display a message that you need to unlock your phone or does it show a black screen? In my case after updating my phone, Phone Link shows a black screen but after I blindly type in my phone password on the PC followed by Enter I am able to use Phone Link as before without touching my phone.
For reference: I am using an older version of Phone Link (1.22102.202.0) on Windows 10 in combination with OneUI 5.1, Android 13 and the latest version of Phone Link on my S21 phone. Using the older version of Phone Link on Windows seems to be the key, so thanks to everyone who suggested this.