LMX2820: LMX2820: Internal Temp sensor ReadBack

Follow the steps below, the MUXOUT output is all 0, and the LMX2820 is locked. What could be the reason?

Steps: 
1、R19 writes 0x132138; that is, TEMPSENSE = 1 
2、0x4C writes 0x4C0000;

Thanks！