Thank you for reply, AurimasV!
The USB cable used during failing communication attempts was exactly the same which was used before with mentioned tracker for previous successful operations like reading config or changing parameters. As you suggested, it was successfully tested with other devices. Moreover, a few other cables were tried but with the same result.
PCB looks fine, as a brand new.
Unfortunately, it is impossible to test Bluetooth connection: tracker has this function turned off.
I suspect that "Status" LED blinking every 3-4 seconds indicates device's booting attempts but with no success. The observed sequence is following:
1) LED blinks;
2) I hear system "connect" sound, virtual ports appear in PC's Device Manager;
3) after 1-2 seconds I hear system "disconnect" sound, virtual ports disappear;
4) go to (1)
Tracker's radiomodule doesn't work obviously because tracker doesn't receive SMS-commands and doesn't respond to calls: when I pull SIM-card from Teltonika and insert it into phone, it starts receiving all skipped SMS.
UPD: firmware version can't be checked anymore but I'm aware of it: 1.03.13.Rev.00