Hello,
I get my CCleaner in "Unregistered" status although my subscription is still valid.
It is a bug and they are working to fix it, please see here for more details and how to roll back to v6.17 if you want to:
I tried also to reinstall it but issue still exists,
I read the red announcement regarding the issue & I understand it is a bug.
hope it get fixed soon.
retrieving to the previous version is the best solution for now.