CaptainPugwash ✭

Thanks very much for this very comprehensive answer . However, I'm not sure it was the right answer. I repaired Bitdefender as per the first step and discovered that my scheduled scans had disappeared. In the process of reinstating those, I found an option to close the scan window on completion if no threats found. See…

I reinstalled as suggested and it appeared to work initially but was not there when I rebooted. That may be part of the problem. Unfortunately I am temporarily away my desktop, so will check it out as soon as able.