Specific Lookup Fails

I have one specific IP address that I am unable to contact whenever I attempt through a device using the T-mobile WiFi.  If I remove my device from WiFi, it immediately works.

Suppose the address is wts.populiweb.com

How do I get T-Mobile to stop failing to resolve it?  I get the error wts.populiweb.com’s server IP address could not be found.

This started about a week ago.

How can I resolve this issue?

Gracias.