"subscribe by email" link on blog posts not working!

Site URL: https://www.experiential-psychotherapies.com

My site has multiple blog pages.   I want people to subscribe to each discussion thread when they leave comments.   I used the squarespace comment function rather than something like Disqus because I thought it would be simpler that way.  But no one seems to be able to subscribe.  There's a button that says "subscribe by email". It brings people to a squarespace sign in/login page that no one seems to be able to get past, whether they log in using email, google, apple or Facebook.  Everyone gets a confusing web of error messages.  

Strangely, I've done it myself with 3 different emails and had no problem.  But over half a dozen people have reported the same frustrating inability to subscribe to threads.  Squarespace support has not been able to fix the problem for me so far.  

What could be going on here?  

Should I be using Disqus or something similar instead?  

I have multiple word docs detailing people's experiences of being unable to subscribe.  The issue is that they can't log in to squarespace.