The site on Flask stopped working correctly after uploading to heroku, what should I do?

Question

MySQL

Hello, this is the thing. When you run the site from your local computer, everything works fine, after uploading to heroku and connecting the database to mysql (remote connection to the database works well), everything stopped working, and there are the following failures:
1) When registering via https://polus-tomsk .herokuapp.com/ no message comes to the mail, while when registering through 127.0.0.1:5000 everything comes and works
2) Even if you manage to log in to the site (which succeeds in 20% of cases), most often when refreshing the page or switching to another, authorization is reset

https://polus-tomsk.herokuapp.com/ - here is the site that uploaded
with other projects where there was no remote connection to the mysql DB, everything was fine on heroku.

I tried to set up SameSite, I thought that was the problem, but as it turned out, no.

Answer 1

1) I had a similar problem, only on Django . It is necessary to specify the correct data of the Email server in the project ( if I'm not mistaken, that's what it's called )
2) If I'm not mistaken, then the session recording failed, which resets the authorization