I agree with Harwich. This is the work-around steps I'm using until such time the latest version of CCleaner is fixed:
Step 1 - Disconnect from the Internet.
Step 2 - Open CCleaner. It should stay open at this point.
Step 3 - Reconnect to the Internet and run whatever sub-program(s) within CCleaner you want.
Windows 10 Pro Version 21H2
CCleaner - The latest version to date.