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HMC Calibration not working

My code is following the steps described in the datasheet under section "RC Calibration Circuit"  Note:  our board has a 50M clock connected to Pin 11 (CALCK) always.

When I check REG8 [4] it is 0 immediately.  When I read the calibration result from REG9[23:0] it is always 0.  Any suggestions?  Thanks.