MC7304 VoLTE support

Hello!

MC7304 Revision: SWI9X15C_06.03.32.04 r28324 CNSHZ-AR-BUILD 2015/05/25 01:09:15

Does not register in the IMS network.
What can cause the problem?
Is there an AT command for forced registration?
Thank you!

at!gstatus?                                                                     
!GSTATUS:                                                                       
Current Time:  211              Temperature: 30                                 
Bootup Time:   5                Mode:        ONLINE                             
System mode:   LTE              PS state:    Attached                           
IMS Reg State: NOT REGISTERED   IMS Mode:    Normal                             
IMS Srv State: NO SMS,NO VoIP                                                   
LTE band:      B3               LTE bw:      15 MHz                             
LTE Rx chan:   1275             LTE Tx chan: 24200                              
EMM state:     Registered       Normal Service                                  
EMM connection:RRC Idle                                                         
                                                                                
RSSI (dBm):    -66              Tx Power:    0                                  
RSRP (dBm):    -94              TAC:         4CE1 (19681)                       
RSRQ (dB):     -11              Cell ID:     0BF0A40B (200320011)               
SINR (dB):      7.4                            

AT!CUSTOM?                                                                      
!CUSTOM:                                                                        
            ISVOICEN            0x01                                            
            PCSCDISABLE         0x03                                            
            GPSENABLE           0x01                                            
            RRCREL7CAPDIS       0x02                                            
            GPSSEL              0x01                                            
            NMEAENABLE          0x01                                            
            GOBIIMEN            0x01                                            
                                                                                
OK                            


Where do you get this firmware?

https://source.sierrawireless.com/resources/airprime/software/airprime-em73xx_mc73xx-fw-package-latest-release/

You can also see here