Having problems while Activating manually - Avast pro 2018

Hey guys,
I brought a avast pro anti-virus 2018. When I tried to enter the code manually it says “something went wrong. Please try again…”… I tried many times, by reinstalling, removing. I tried multiple times. But couldn’t succeed. Please help me. It’s really frustrating. I have tried many anti-virus but this is really annoying.

See if this helps:
https://support.avast.com/en-us/article/Troubleshoot-activation

Thank you. But I tried that as well. But nothing really happened. Sometimes, the error comes immediately after I enter the code, sometimes it comes while registering my details.

Contact Avast customer support:
https://support.avast.com/en-us

Hi, see: https://forum.avast.com/index.php?topic=219020.msg1461635#msg1461635