Can you please delete that link to our portal from your post ? That's one of the reasons why I privately sent the HAR file and obfuscated URL in the screenshots...
This is an enterprise grade installation so I have no use of the platform if it doesn't support SSL. However the previous install on the previous server was running SSL like a charm with these certificates.
I'm currently using free SSL certificates generated by certbot / letsencrypt.
I've created a new user, the invite was sent to firstname.lastname@example.org
Please keep me updated