1.Incorrect upgrade will damage your device.
2.Please upgrade your device by cable connection.
3.This firmware can solve the problem about wireless WAN.
4.You can upgrade from V2.XX.XX or V3.1.201d to this firmware, but it can not be upgraded back to V2.XX.XX.
5.Do not power off the device when upgrading.
6.Please unzip the file you downloaded and use the file ended with "bin" or "trx" to upgrade your device.
7.After upgrading, please restore it to factory defaults and configure the device again.