The program was purchased and the activation code was sent to me. When I open the program and enter the activation code, an error code appears

CCleaner for Windows CCleaner Windows Help Requests
1

The program was purchased and the activation code was sent to me. When I open the program and enter the activation code, an error code appears.

2

Are you typing the key in?
Mistakes can be made when typing (eg, S instead of 5 or the other way round) so we advise that you copy/paste it from the email.

See here for more advice: CCleaner Support Community

If you are still having problems after following the advice there then please come back to this thread and ask for more help.