Hello Herbert,
It does exist since the BTS is like 4 meters from the device. Also I have tried the NBAND command but I do not know which band is correct.
Hi,Qesk:
BC68 supports B1/B3/B8/B5/B20/B28, and your virtual base station needs to be configured with the corresponding bands
Hi Herbert,
I know these are the supported bands but what band should I use? Also shouldn’t I set AT+CEREG=1 to register?
Hello Herbert,
I came to the school and restarted the BTS and module as well. Configured everything all over again and it is working. I have my IP address assigned and everything is running. Now I need to just make MQTT woking 
Thank you for everything.
Hi Quesk,
T-Mobile is using Band 8 in Europe (Vodafone = 20). Setting this, speed up the network register a little.
On the other hand, check AT+NCONFIG?
The settings CR_0354_0338_SCRAMBLING and CR_0859_SI_AVOID have to be true. This is important in T-Mobile network.
The BC-68 is really slow registering to network. Here in Dresden, it took 30 - 200 seconds. Maybe you are too impatient 
The BC-66 in contrast need 2-5 seconds for the same.
Best Regards, Andreas
Please refer to the following documentation for MQTTS. Our MQTTS all support standard solutions
Quectel_BC66&BC66-NA_MQTT_Application_Note_V2.0.pdf (3.7 MB)