Had you restarted your Emby Server when you disabled external access ?
Tested the previous solution in Emby link provided in previous post, for the Emby Apple TV app to see if that works with MrMC.
iOS:
No manual and pin-request sign-in MrMC.
In Emby iOS app it all works by manual sign-in. Even Safari web browser access from iPad to my local server in safari tot IP:8096 works with manual sign-in.
tvOS:
Only pin request sign-in works.
In Emby tvOS app it all works by manual sign-in.
Seems like MrMC doesn't like Emby WINDOWS server or the other way around