I bought a used M8. It is unlocked. It currently has a outdated version of software. Software number is 4.18.... When I checked for software updates, it says the phone is up-to-date. Please help me to get my phone updated.
I downloaded the update for Unlocked/Developer model and tried to update manually, but it says Error 155 : Unknown Error. The ROM Update Utility cannot update your Android phone.
I searched the IMEI info for this phone. Part description says it is a USA device, AT&T, with SIM lock.
Therefore, my assumption is that the phone was AT&T locked but was subsequently unlocked. Could you please advice me on whether I should flash an unlocked ROM or is there another safe way to get it updated?
Thank you in advance