That sounds like you have updated to CCleaner 7 and are stuck at the Welcome screen.
We’ve had lots of reports of this welcome screen issue and there’s a work round (it works for most):
Go into Windows Settings and set the display scale to 100%.
Run CCleaner 7 and get past the Welcome Screen.
Set your display scale back to what it was.
I anticipate that once you do get CCleaner 7 running you might then have another question to ask, so:
How to Roll Back from v7 to v6.39