just downloaded the version of your website. but say's it is illigal version

i bought the avast premium security yesterday. but now it is showing a message that it is a illigal version of the software and i have to but the real version.
but i did? how to solve this problem? :o

Posting a screenshot of warning messages is always a big help, so we can see what you see

You also didn’t say where you bought the product.

Are you sure you downloaded it from the ACTUAL avast company? Normally, that message appears if you download a cracked version (if you downloaded it from PirateBay or something) and if you didn’t crack it, did you download it through the avast app itself/real website? It would also be helpful if you give us the domain where you downloaded avast from.

Does this matter a great deal?

Identifying and preventing fraudulent sales of Avast products
https://support.avast.com/en-ww/article/26/

It certainly does.