I am not receiving activation mail for Docker Hub account sign up. I tried resending the email and resetting my password. Neither of these work. Please help. This seems to be an existing issue from long back 
You can try to report it on GitHub or find a recent open issue to add that you have the same problem:
Does it mean you changed the email address? Make sure you have a trusted email provider and check the spam folder too. Unfotunately this is all I can recommend