Synapse Letsencrypt

I haven’t been on the forum for years because everything has worked perfectly for years so I apologize for not knowing how to post
Just a fairly simple question.

I have installed Synapse and it connects fine on lan but not over the internet with element. I think I need to manually create a TLS certificate.

My domain is example.com but I am using matrix.example.com because it sits behind server with NPM.

The Element app spits out can’t trust.

Thanks

Did you already tried creating a SSL certificate within NPM?

First thing I did. On install at the newuesr localport I use default root, ok for that?

Solved Thanks

One last question, how do I enable registrations?

Did you already checked official synapse docs? Configuration Manual - Synapse