Modal Login disables registration_errors hook

I did not post this in the Modal Login forum because the newest post in that forum is about 7 years old! I am using Modal Login for a small HOA site that I am developing, because I want a popup login form and neither I nor the HOA’s funds can afford lots of paid commercial plugins. Modal Login works fine and does what I want to do, but I now want to add some email address checking – basically our owners (whose email addresses we know) should be able to register with minimal formality, but others should have to go through me and be approved by the Board. I have tried hooking registration_errors and register_post – neither hook appears to work with the Modal Login login/Registration form, but I know that my code is correct because if I force the use of WordPress’s native login/Registration form, my code runs and does what it is supposed to do.

Does anyone know of a way to hook into the Modal Login Registration code for this sort of purpose? Alternatively, does anyone know of a current free plugin that can be substituted for it and complies with WordPress’s protocols in this area.