I got an issue to register myself. (Ofc I post here so I finally succeeded)
Problem description:
The mail contains a link to follow, this link got a token inside, most probably a once I guess. The issue is that token was surrounded with square brackets and also an url encoded "=" ("%3D")
When I played the url straight, it lead or to black screen or to another registration mail being send (loop)
I succeeded by stripping the square brackets, removing the encoded = and played the resulting url in privacy mode enabled tab...
Looks a little bit cumbersome to register

Happy to be part of your community, thanks to read me.