[Kumba42]

I recently got an unlocked Keyone (GSM) off of Amazon, running the June OS update (AAL964), and signed up with T-Mobile on a prepaid account. I have had virtually no issues and this has been a nice upgrade from my older phone, which I had for ~4 years. Under T-Mobile, I have tried to use several of their "short codes", such as #BAL # (225) to check my balance or #WEB # (932) for data usage. However, none of their specific codes work.

I first get the "USSD code running...", followed by an error message that says "Connection problem or invalid MMI code". I have tried a variety of things, including powering off, pulling the SIM card, restarting, powering off again, and putting the SIM card back in. I have also opened a ticket with T-Mobile, however they have indicated that everything works on their end and closed the ticket.

Has anyone else had this issue and perhaps know of a solution? I've also accessed the testing menu and looked around, but nothing really stands out to me. For all intents and purposes I have no issues with this phone on T-Mobile. The only thing I did notice is the phone does not know what its assigned phone number is, but it will receive calls or texts placed to that number.

[portplayer]

I think the prepaid sim card might not be right for your plan/device. For instance Verizon (albeit I use the postpaid plans) has two kinds of nano sim cards. For whatever reason device activation wouldn't work on one, but would the other. Idk just my two cents. Good luck!

[varasani]

I recently got an unlocked Keyone (GSM) off of Amazon, running the June OS update (AAL964), and signed up with T-Mobile on a prepaid account. I have had virtually no issues and this has been a nice upgrade from my older phone, which I had for ~4 years. Under T-Mobile, I have tried to use several of their "short codes", such as #BAL # (225) to check my balance or #WEB # (932) for data usage. However, none of their specific codes work.

I first get the "USSD code running...", followed by an error message that says "Connection problem or invalid MMI code". I have tried a variety of things, including powering off, pulling the SIM card, restarting, powering off again, and putting the SIM card back in. I have also opened a ticket with T-Mobile, however they have indicated that everything works on their end and closed the ticket.

Has anyone else had this issue and perhaps know of a solution? I've also accessed the testing menu and looked around, but nothing really stands out to me. For all intents and purposes I have no issues with this phone on T-Mobile. The only thing I did notice is the phone does not know what its assigned phone number is, but it will receive calls or texts placed to that number.

I too had this problem in my previous keyone. I got a replacement when my fingerprint sensor stopped working and the new device was in factory firmware. It worked in that. Then after update to AAL964, it works sometimes other times I get the MMI error. At least it didn't consistently throw an error like my earlier keyone did. Might have something to do with cell tower or signal. Try changing to GSM only bands and run the USSD code. I run the #932 # on Tmobile to get data usage.