MC7354 low power mode

Hi,

I have 1pcs MC7354 works in low power mode.

AT!GSTATUS?
!GSTATUS:
Current Time: 58 Temperature: 24
Bootup Time: 0 Mode: LOW POWER MODE
System mode: Unknown PS state: Not attached
OK
AT!PCINFO?
State: LowPowerMode
LPM force flags - W_DISABLE:0, User:1, Temp:0, Volt:0, BIOS:0, GOBIIM:0
W_DISABLE: 0
Poweroff mode: 0
LPM Persistent: 0
OK
AT+CFUN?
+CFUN: 0
OK
AT+CFUN=1
ERROR

What’s the possible reason that the modem become low power mode?
How can I active the “online” mode??
Many thanks in advance!!