Avast: Cannot Insert Licence

Hi All

I’ve just bought 20 licences of Avast Endpoint Protection Suite Plus for, and it has emailed me a licence file. When I go to add it to Avast, of which we have the free edition, it says “Cannot Insert Licence”.

How do I upgrade the software?

Edit: I have uninstalled, using the clean software, and re-installed on two PCs now. And still the same error.
This is on Win 7 machines.

FAQ search and find >> https://support.avast.com/support/home

https://www.avast.com/faq.php?q=endpoint&authenticity_token=RCHA96xwKLLPgO69s%2BujXQJZi%2F9rlxf0Kgze8ABQn3c%3D#searchForm