How can I make password reset work for DNN 7.3.2 / Dynamic forms 5.0.41?

I have been battling password reset not working on my site since it launched two weeks ago (I have had multiple calls and tickets with DNN support). My dnn site is 7.3.2 and my Dyamic login version is 5.0.41. 

Password reset works for anyone who has registered for the site since we went live, but not for any of the many users imported from the old site. A user can request a password reset, but once they follow the email link they get an error that password couldn't be changed. Nothing shows up in event log about it. 

Today I tried using the built in DNN account login module and discovered that login module functions properly when requesting a reset link. 

Their module obviously leaves a lot to be desired so I would really prefer to use Dynamic Login, that is why I buy every upgrade…. but it looks like the dnn account login might be my only option. Do you have any known issues or advice on how to get this to work?

Note…as a test, I tried using the password reminder link on this site and got a 404 error when i clicked the reminder link I received in my  email.