1.This firmware have added the function of roma.
2.This firmware have Optimized the APN of Romania & Germany and Austria.
3.Unzip the file you downloaded from Tenda website and the correct format of firmware is end with".tar".
4.Incorrect upgrade will damage your device.
5.Please upgrade your device by USB cable connection.
6.Do not power off the device when upgrading.
7.After upgrading, please restore it to factory defaults and configure the device again .