Nano Sim to Micro Sim Adapter = no data?

[onthecouchagain]

How come when I use my Nano sim in a Micro SIM adapter for the Nexus 5, I get no data? I can do calls and SMS just fine, but no data.

The nano SIM is coming from a Galaxy S6. Tmobile. Any thoughts? It shows "Tmobile" in my status bar, but there's an ! sign next to it too.

Any help would be appreciated.

 

[mrsmumbles]

Did you add the T-Mobile APN?