UPDATE
About the Sensor Threshold Crossed error.  When I went and upgraded the RAM on another B200 M4 blade, the Total Memory was 786432 and 786432 for the Effective Memory.  The first RAM upgrade, the Total Memory was 786432 and the Effective Memory was 753xxx(don’t remember the rest).  When I subtracted the values it was 32xxxx.  So I powered down that blade and re-seated all the memory.  When I put the blade back in the slot and UCS was provisioning the server the Total and Effective were now the same.  So somehow (and I double checked) one stick wasn’t seated properly.  Luck was on my side that day.
UPDATE

To supplement our growing need in virtualization, it was time to upgrade our six Cisco UCS B200 M4 memory.  The blades originally came with 256GB of RAM with 16GB sticks(16 slots used).  Updating to 768GB RAM with 32GB sticks.  This will fill all the slots for both processors.

After the upgrade and UCS reprovisioned the slot, there was a memory error, but the server still booted up.  DDR4 ECC Sensor Threshold Crossed.  To correct this I had to login to the fabric interconnect and changed my scope to the affected server.

scope server 1/1
reset-all-memory-errors
commit

https://www.cisco.com/c/en/us/support/docs/servers-unified-computing/ucs-b-series-blade-servers/200775-Troubleshoot-DIMM-memory-issues-in-UCS.html

By Tim