users cannot login

I have a problem with a website where users buy a course and get access to certain pages. I work with Elementor and the theme Astra. When I try to login as a user with access to the page, I get the error ‘Undefined’ and in the inspector I see this:

Failed to load resource: the server responded with a status of 400 (Bad Request)
/wp-json/aam/v2/authenticate

and

Uncaught TypeError: Cannot read property ‘querySelector’ of null
at cbpHorizontalSlideOutMenu._init (frontend.min.js?ver=1.1.6:408)
at new cbpHorizontalSlideOutMenu (frontend.min.js?ver=1.1.6:398)
at frontend.min.js?ver=1.1.6:499
at frontend.min.js?ver=1.1.6:501
at frontend.min.js?ver=1.1.6:503

What is going on?

The page I need help with: [log in to see the link]