I bought a 2 years license extension for CCleaner yesterday and tried to send the cashback request today.
Problem: the ‘Next’ button to the final step 3 on the website is dysfunctional after I have entered the required data.
It is not possible to send the request. And: the support form that is linked on the website is not existent (error: ’ Form is not available for your language!'). I tried several langages, without success.
I need some advice please. Thanks in advance 
Cashback offers usually have a time/date before which you can’t apply.
Everybody has to wait untill that date before they can apply
The button(s) on the application will not be active before that date.
Check the Terms and Conditions on the cashback offer which should give that date as the start of the ‘Claim Period’.
Once that date has passed then there is also a FULL 24 hours after purchase that you should wait
See: How it works
That 24 hrs is needed for your purchase to get fully registered at the company running the cashback promotion.
Until your purchase is fully registered the casback firm won’t recognise it.
If you try to apply earlier than the offer terms state then it won’t let you.
Check your purchase confirmation email, there should be a ‘How to claim your cashback’ link in it which will tell you how long you need to wait before applying..
PS. That ‘Form is not available in your language’ error for the CCleaner support form is known about. Once you have the error it won’t even let you go back to English.
Close the webpage, open the English form again, and use the English form without trying to change language.
Had no luck in completing the Cash Back form or contacting support. Final button remains greyed out and contact form is not available. I’ve not found any way to reopen the form in English as you describe.
My problem has now been solved. I contacted support@ccleaner.com. They replied within 3 days with a short workflow to apply for the cashback. This workflow didn’t help, so I sent them a 2nd mail with screenshots of my Ccleaner account information and the greyed out ‘Next’ button on their website. The support then sent me the cashback manually within a few minutes.
Thanks for letting us know.