Network registration fail

Hi, i have a problema with a wismo228 model . when i try network registration modem continuosly connect and disconnect from network: it remain just 2 seconds conneted.
at +creg=2
OK
+CREG: 1,“4E3C”,“5797”
+CREG: 0
+CREG: 2
+CREG: 1,“4E3C”,“5797”
+CREG: 0
+CREG: 2
+CREG: 1,“4E3C”,“5797”
+CREG: 0

first I thought to check antenna and signal quality:
OK
at+csq
+CSQ: 0,99
OK
at+csq
+CSQ: 0,99
OK
at+csq
+CSQ: 21,99
OK
at+csq
+CSQ: 0,99

and checking cind ( second bit should be signal quality )
OK
at +cind?
+CIND: 0,0,0,0,0,0,0
OK
at +cind?
+CIND: 0,4,0,0,0,0,0
OK
at +cind?
+CIND: 0,4,0,0,0,0,0
OK
at +cind?
+CIND: 0,0,0,0,0,0,0

i also check cell information( six value should be rxsignal level)
AT *PSENGI=0
*PSSCI: 0,7,-5843,4100,45,0,0,0,0,0,0,0,0,0,9,0,0,0,80
AT *PSENGI=0
*PSSCI: 0,7,-5843,4100,45,0,-582978353,2290177,222,10,25003,0,255,0,9,0,255,255,80

this module is conected only with a sim module, serial tx rx gnd rs 232 interface, antenna.

what do you think ? anyone can help me ? any suggestions, other commands to check, all is welcome !

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