I'm using HTC One M7, Android version 4.2.2, not rooted.
After trying to change the preferred network type using the special "*#*#4636#*#*" "Phone info" screen, and restarting the phone, my IMEI was erased (it now appears as all-zeros). Also, my MEID (under "Phone identity") is now 00000000.
Is there any way to recover the IMEI except a factory reset? Will a factory reset even help?