Critical Error on Website

It began when suddenly a plugin that sends invoices by email after a transaction is completed, stopped working. We checked the backend – and this showed up

Other areas also affected – both at the backend and frontend.

#1 – the page looks like this right now – https://www.curedemy.com/

But on the backend, while editing on elementor – it looks like this:

And on the backend, when trying edit user role, the error shows up again:

The error seems to be expanding. At one point, the entire site showed the same error – and the website was not even opening. I have deactivated most of the plugins right now to bring the website back. If I activate all plugins, the error comes back. I read that if memory limit is affected overall, this error may appear. So, I was trying to figure out the site’s memory limit – through wp-config file, php.ini as well as .htaccess file.

This is php.ini file.

This is .htaccess file

This is wpconfig. It originally did not contain a line of code for memory limit – but I added at the last.

The issue still remains the same. The below hasn’t changed.

How to troubleshoot this error? Is this error really about memory limit?

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