Just applied the newly released version of wpforo 1.4.12. hoping it might be the fix.
The problem still persists, although rather than stating "invalid key" the link just takes you to the forum homepage as does absolutely nothing!
Until this is fixed I've had to install a third-part registration plug-in
Just tested it and seems to work just fine on my site.
Just thought I would say that I'm having this issue as well. In fact so is this form wpforo.com! I just registered on it, the link it sends takes me to this site, a message pops up saying the key is invalid. I had to click lost password in order to be able to set a password and login.
No problems here, but I use SendGrid for all emails instead of relying on PHPmail.
I receive e-mails too, despite the title of this thread, its not about not receiving e-mails.
Its the fact the received reset key within the e-mail was first invalid as evidenced by my attachment above in this thread, and then after 1.4.12 the key did nothing at all!
I've now disabled wpforo registration, login and password reset for another third party plugin. The keys supplied by that plugin work. It allow users to register and reset their password.
Clearly for some wpforo clients, the key process is broken.