You have reached the limit of custom field allowed in your database

is there any thing I can do to put this to the test ?

Its a bit hard to tell without looking into the server and instance itself.

If mautic is behind reverse proxy you have to make sure to tell that to the web server by setting appropriate request headers.

I would also check what is the actual response of the server when you get the error.

If I recall correctly when using reverse proxy you would have to set something like:

$SERVER['https'] = 'on';

But all that is just guessing without looking into the server and mautic config.

I am more than happy to look into that in scope of my services. Please drop me a DM if you are interested.

Best, M.

Best, Mat