So I went to use my CCleaner Professional and checked for update, says there is one, so I click on it, and it wants me to purchase? (may account says re-new is September 2021) so I guess I am confused to what happened? This is a home computer that I use occasionally.
Where it asks you to purchase click on 'No Thanks' and carry on from there.
If you download/install the free version it should recognise that the one you are replacing is Pro and register the new installation as Pro.
If for some reason it doesn't (say if you had uninstalled the old version) then go to Options>About and click 'Upgrade to Pro'. That gives a box where you can enter your already registered name and key then click on 'Register'.
There is not an option for 'No Thanks'
Where would I install free version? Why would I need to re-install?
I tried to register using my name and key and it says 'not valid' or something to that ...
OK, use this link to download CCleaner, the "slim" does not contain any bundled offers so it's what most of us here use:
https://www.ccleaner.com/ccleaner/builds
Simply download it and double click it to install/update the latest version over your current version.
The invalid key thing is probably something we see a lot. Be careful not to mistake letters for numbers - I & 1, Z & 2, S & 5, B & 8.