In fact, we have several issues related.
0. When I try to make Dump in Teltonika.Configurator (1.7.4 B.FM64 R.12) to help problem resolving, it gives the following error message:
"Response Id from device does not match with expected response Id. Receive response - FileManagementRequestResponse, expected response(s) - Ack"
1. Basically, the FMM640 doesn't use 4G. Parameter #178 = 1 indicating 2G mode. I've tried all possible combinations in Network Settings. If I use "Auto", the device falls back to 2G. If I force 4G (with any network modes or band selection), the device simply cannot go online. The SIM card is OK, it uses 4G if we put it in a phone. [GSM operator is Telenor HU.] The signal strength is excellent both in 2G and 4G.
2. I've tried a different SIM card (from Vodafone HU). FMM640 couldn't go online at all. Not even in 2G mode. No error codes or error messages. Needless to say this card works perfectly in a phone.
Do you have any settings, parameters or logs to check why our FMM640 is unable to use 4G (or go online with the Vodafone card)?