HomeAssistant Companion App issue?

I have had to reconfigure TailScale after a recent update to work while away from home again.

After the new setup detailed by TailScale and also on HomeAssistants integration help page, I can only access the UI through my browser using my MagicDNS, and not the companion app.

I am running my HomeAssistant as an exit node with Serve enabled.

I have my MagicDNS as the External URL hence why I can access in browser. I still have the standard Local IP for internal connection on my WiFi at home.

I'm confused as to why the External URL will not work with my companion app now as before the recent update, it was working fine as long as I connected to the exit node.

Am I missing something or is this odd?

Thanks in advance. Please be gentle, I am an industrial maintenance electrician who works with PLCs, I am new to this back end server stuff to run my automations.