[One (M9) Q&A, Help & Troubleshooting] DigitalBeating:
Hi, my sister bought a used phone off eBay. When she got the phone it needed a Nano Sim and she converted her standard sized sim into a Nano Sim with the help of T-Mobile and installed the sim card. Everything went well until her husband went to buy a Galaxy S6 used off of someone on Craigslist and he took her Nano Sim out and put it in that S6 to test the phone. But when he put that Nano Sim back into the HTC One M9 the phone stopped working and says "Limited Service." The phone shows the phone number on the sim correctly and all the contacts stored on there show up but there is "Limited Service." Manually trying to select the service provider says "Your sim card is not authorized on this network." But taking the sim card out of the HTC One M9 and testing them in a Lumia 950XL, and Galaxy S6 it works perfectly fine with data and calls. Also testing the working sim cards from the Lumia 950XL and Galaxy S6 on the HTC One M9 results in the same "Limited Service" notification on the phone.

Things I have tried:

1. Putting tape in the sim card tray to increase the height of the sim card so the pins make good contact

2. Setting the APN manually or manually selecting the network

3. Testing the sim card on another phone

4. Testing working sim cards from other phones on the HTC One M9

5. Re-flashing the official 6.0 update from HTC - RUU_HIMA_UL_M60_SENSE70_TMUS_MR_TMOUS_3.39.531.7

6. Turning Airplane Mode on and turning it off to attempt to get the phone to connect back to the network

7. Disabling all other wireless services i.e. Bluetooth, Wi-Fi, etc...

8. Removing the sim card and turning the phone off and waiting 5 minutes, putting the sim card back into the phone and powering the phone on

9. Removing the sim card and turning the phone off and waiting 5 minutes, and then turn the phone back on and then inserting the sim card

10. Booting into the phones modes and wiping all data and cache and restarting the phone

Pretty much I am at a dead end here with this phone. It seems to be a re-occurring theme with the HTC One phones where you end up with the "Limited Service" notification. Long hours of Google research yielded that there were problems with the HTC One M7 & M8 having the same notification issues. I was going to attempt to unlock the bootloader in order to flash custom roms onto the M9 but HTCDEV's website has a broken registration button that is linked to an HTML anchor (#) and submits no data from the form into their database so you can actually register. Attempting to use the WayBackMachine to see what that button was linked to yielded no help at all as it was still linked to the # anchor and pointed nowhere. As in HTML the # anchor just makes the page jump all the way back up and submits no form data into their database for registration. In this case it just jumps to the top of the page and erases all data filled in the registration form.

So pretty much I've exhausted all my resources and the only answer is to get access to HTCDev's website to unlock the bootloader but the registration process is broken for quite sometime now. I suspect the problem is either with the latest update or broken hardware but cannot confirm as I can't install any custom roms to test the hardware. The only other option right now is to take the phone apart and see if there is any loose parts or damage inside the phone but I don't have the correct torque tools to remove the screws.

Any help appreciated.