p607t lte/wcdma not working

I have received a p607t tablet, it was flashed by smb. to p905 firmare (with no imei). i re-flashed it with stock P607TUVUBOI2 firmware (4 files, so-called "service" firmare), imei is back (to what is printed at the back-side) but mobile networking *still* doesn't work: no connection. I'm using not t-mo sim-card, but looks like the tablet was already unlocked

From service menu *#0011#:
SERVICE : LIMITED
NETWORK : UNBLOCK
IMEI Certi: PASS, 1

From Advanced Signal Status:
Carrier:
Network Type: Unknown
Signal info: n/a
Neighboring CID: no neighboring cells --- wtf? >> other devices work ok with this sim in lte and 3g modes<<
GSM service: emergency calls only
GPRS service: disabled

Any ideas?