Not able to connect to server via internet, works locally

https://manual.calibre-ebook.com/server.html

I am using the above as a guide. I managed to connect to the server fine while on the local network. Can I assume if I got that to work then my port forwarding settings are okay?

I run into issues when I try to connect to the server via the "internet". I looked up what my IP is (I don't think its a static IP...which could be an issue) but I get nothing via this method.

Anything else to consider not mentioned in the guide?