I had this issue with several units.
Check the Serial number.
If it looks old (like starting by 11022), you probably had an old hardware revision that was defective.
I am trying to get Teltonika to admit this fact through several distributors, but without success.
In the end, I will buy Huawei or Multitech or Sierra, and they can go to hell.
It is quite simple: if your unit's behaviour is completely strange (no DHCP IP after factory reset, or WebUI not displaying etc...), don't waste any time (I lost a total of 2 or 3 days in the last weeks), send it back, ask for a refund, and then, depending on your dependance to Teltonika:
-try to buy another one
-switch to another brand
David