I have used the Free version for a while with no issue. Today however, I am unable to run the cleaner on custom scan, unless I give my credit card details for a 'free' try. This is beyond sneaky haha, it's like you guys aren't even trying anymore.
Ongoing thread. You are not alone.
https://community.ccleaner.com/topic/67171-ccleaner-62411060-will-not-do-a-custom-clean/
I was able to disable the paywall by poking around in the registry.
Change this value from a 1 to a 0:
Computer\HKEY_LOCAL_MACHINE\SOFTWARE\Piriform\CCleaner\(Cfg)CCNU