SyncUp Kids stuck at loading screen

If the only thing it’s going is T during load and then shutdown, and if you already tried to reset it (hold the button 10 secs) then the only option you have is a replacement in the real T-Mobile shop.
Hopefully they’re not wasting your time after buy to get additional $20 from you for a “warranty” replacement.

I found this thread while looking for a solution for the exact same problem. It is unexecptible that the only solution is for the consumer to pay for a know defect. 

My daughter's watch is now bricked because of something wrong with the watch. Like the OP said The watch doesn't respond to anything. The only thing you can do is hold the button for 20secs or so and it will buzz and hard-reset, then get to the loading screen and sequence the three pink dots on the bottom indefinitely.

And the very next reply from customer support is to factory reset through the UI...haha! Clearly TM has no odea what they are doing and is selling a product that is defective. 

Either TM replaces this watch or I will replace TM with a company that will treat their customers better and own their mistakes.

I feel as though T-Mobile has scrubbed the internet of this issue. I had the issue after an update. I was told to pay a small fee for a new phone. 1st lie. The phone was not new it was refurbished and had the same exact error! I was so mad I didn't even want to deal with calling again. So I let it charge, tried rebooting and let it sit bc life is busy, and then I finally called tonight. I was transferred to 3 different people (likely in India). But one nice manager said he will work with engineers and said it is a known issue.

 This post says resolved, but I do not see a solution anywhere. I want to cancel this service (really I want it to work but if it doesn't work I want a full refund from the original update when the phone stopped working. It has been months and I have not been able to use the phone to track my kids. 

 There are no bars. All it says is not activated correctly, REBOOT.  If I tap the reboot screen a bunch of times it says it needs to be factory reset and says do you want to see the demo yes or no. If you say no it offers rebooting again. If you say yes it goes to a # pad screen and you can enter 4 digits. I do not know a code for this screen. When I tried to see if I could pair it without the right pairing screen coming up on the phone it could not find the phone to pair. I tried to manually input the item number on the back of the phone on the kids sync page online and it still couldn't recognize the number. I tried to scan the TINY QR code which also didn't work. The phone is a rip off, paying monthly for a service and phone that do not work. I cannot imagine if my child needed to reach me bc of kidnappers or active shooters or they are lost and the phone just wigs out on them and becomes completely useless. Oh, but I can imagine them without one completely because that's what is happening now. (2 boys share 1 watch bc they go to the same school and ride the same bus they are together all the time).

 I really hope this supervisor actually finds an engeneer who can fix the reboot issue or give me a full refund. They can see howblong it has been since we have communicated using the phone and this is not something we did. It is a product issue and I am paying monthly for nothing! If this guy figures it out I will be thrilled and share if I can ever locate this validating thread again. May the odds ever be in our favor.

Same issue here :(