1. dblazer321's Avatar
    Hi All

    So I recently obtained a new Nokia Lumia 925 locked to T-Mobile and unlocked it using a code from cellunlocker(.net) so I could use my active AT&T SIM card. The unlock code was accepted and my AT&T SIM card started working for ~1 hr and I upgraded the phone to 8.1 developer preview. It worked fine on 8.1 when all of the sudden, the phone came up with the 'SIM Error The SIM card is missing or invalid etc.' I restarted the phone and the SIM card started working again before coming up the the 'SIM Error' again after ~20 min. After restarting again, the same issue occurred and eventually the phone did not recognize the SIM card at all.

    I tried hard reset several times yet this did not fix the issue. I also downgraded the phone to windows 8 using the nokia software tool and the SIM card was again recognized but for only ~5 min. After many hard and soft resets, the issue is not resolved and I have no idea what to do. A T-mobile SIM card did not seem to be recognized either when I tried though the SIM card was not active (it was, however, recognized by my iPhone 4). I did not buy the phone from a store so I will not be able to swap the phone for a new one.

    I would very much appreciate if any of you have input
    06-23-2014 10:14 PM
  2. AlastorX50's Avatar
    Have you downloaded network+ for your phone? There are settings in this application that use carrier settings and apply them to the SIM card.

    Also make sure that all the system apps are up-to-date.

    Hope this helps.
    Last edited by AlastorX50; 06-24-2014 at 01:09 AM. Reason: Added extra work
    06-24-2014 12:54 AM
  3. gedzum's Avatar
    Since it only works for a few minutes/hours, it could be a problem with the SIM card and/or the slot itself. Considering the SIM card worked on another device, I may speculate the problem to be the latter.
    06-24-2014 01:01 AM
  4. Andrew Anglin's Avatar
    I'm glad I stumbled across this as I just got the unlock code from ATT for my 925 and am having the same issues. I'm trying to use a SIM from Personal in Argentina that I know is good as I took it from another Lumia here that has service. I'm going to play with the network settings and see if I can't do anything that way before getting a carrier involved. Will post again if I find a solution!
    07-28-2014 05:03 PM

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