My new iPhone X doesn't let me enable cellular on my Apple Watch Series 3. it fails with the error "Unable to configure Cellular Plan". See the attached .gif for the whole process.
T-Mobile technical support also seem clueless about this. Even resetting the apple watch and setting it as a new watch (or restoring from an existing backup) fails to configure cellular on the watch. I can skip cellular and continue the setup just fine and watch works as expected in all other areas, excep cellular can not be enabled.
Best answer by decent4u
After a long week. This issue was finally resolved by providing the watch EID number (found in watch under General->About->EID) to the support rep. I was helped by Elizabeth from TMobile Customer Support. She kept me posted me on the issue and was finally able to figure out there's a manual way to reset it with EID (on Tmobile side). Elizabeth, thank you! I'm a happy Tmobile customer who can use his Apple Watch Series 3 with Cellular again! 😊