Hello!
To my understanding, my unlimited subscription should allow me 21GB of data in EU countries. However, my eSIM is not able to connect to the Hungarian networks, be it manual or automatic. Note that my issue isn't just no data, I literally cannot connect to the network, and thus I can't use the dial-to-enable codes.
I've checked my account settings and as far as I can see everything is how it should be. I've tried restarting the phone and disabling and enabling roaming data through the device settings & the My T-Mobile app.
As a point of reference, I have a Pixel 5 and trying a local SIM card allows connection perfectly fine. This is a pretty urgent issue as I need my network connection throughout my stay.
All the best!