Have you tried some basic network tests from the device that is connecting to the hotspot?
Since a hotspot is turning your device into a router, simple things like ping or traceroute can start to tell you some basics of if the configuration is correct.
Also check your connected devices default gateway and make sure it matches your wifi hotspots IP as given to your connecting device.
EDIT: I just checked and there are indeed SOME plans from T-Mobile that don’t include support for hotspots. Check your plan to make sure, and then try the workarounds from /u/lukmly013
Have you tried some basic network tests from the device that is connecting to the hotspot?
Since a hotspot is turning your device into a router, simple things like ping or traceroute can start to tell you some basics of if the configuration is correct.
Also check your connected devices default gateway and make sure it matches your wifi hotspots IP as given to your connecting device.
EDIT: I just checked and there are indeed SOME plans from T-Mobile that don’t include support for hotspots. Check your plan to make sure, and then try the workarounds from /u/lukmly013