I purchased a license for CCleaner Professional. It did not come up with a place to enter the license #. I went to OPTIONS>ABOUT>REGISTER and nothing happens when I click on REGISTER so I am unable to enter my license # and cannot use CCleaner Professional. I have no idea of where to go from here. Hope you can help or I will cancel my subscription. Please advise.
I have the same problem (9/24/2020). Nobody has replied to you with a solution ?
The op of this thread was doing it the wrong way round, you have to enter you key and then click register.
The sequence is Options>About>Upgrade to Pro>{enter your key}>Register.
You also have to enter your registered name in a seperate box that pops up - the same name that you used when purchasing.
(Older versions may ask for the name and key in the same box).
Be careful not to have leading or trailing spaces in the name or key.
Also be careful not to confuse number and letters in the key, eg. 'S' and '5' can often be confused. (It's best to copy/paste the key from your confirmation email).
See lower down this page for more details and screenshots: