The one-time link to verify switching if clicked on and not completed should be reset to allow it to activate or be resent until it is completed. Perhaps to be on the safe side a message with a time-out period of say a few mins (e.g. your link is being reset/resent? please try again in a few minutes)
Failure to complete is causing much angst and a lot of wasted time for new joiners many of whom question or regret their switch when this fails, so it’s not a good start. The only plus side is that it drives some to the community, but sadly not just to introduce themselves.