Mac Pro 6.1 (Macs Fan Control AND TGPro) unable to control fan after riser board replacement.

On my Mac Pro 6.1 (trashcan) I previously installed Macs Fan Control and it worked perfectly. I proceeded with a processor swap during which I inadvertently ruined my processor's riser board. I purchased a used replacement riser board and installed it with my processor of choice and reassembled. Everything works fine except Macs Fan Control. This app reads the sensor temperatures, but shows 0 rpm for fan speed. The fan IS spinning, at what appears to be the stock speed. Macs Fan Control (paid version) is unable to control the fan at all.

I removed Macs Fan Control and installed TG Pro and have the same problem. TG Pro is able to read all of the sensors but shows 0 rpm, even though the fan is spinning. It states, "TG Pro is successfully connected to the fan helper app which is required for fan control." Yet,,, it's not controlling the fan!

With 2 apps each unable to control the fan and both failing in the same manner, I have to assume the fault lies with my Mac Pro. I'm wondering if there is a problem linked to using a different processor riser board.

This Mac Pro 6.1 is running Sonoma 14.5 using open core legacy patcher. My processor was previously the E5-2697 V2 12 core 130W CPU; I replaced it with the E5-2673 V2 8 core 110W CPU, for the purpose of lowering heat production in this unit. This Mac Pro has 64 Gigabytes of RAM and it's stock 500 Gigabyte SSD. It's running it's stock Firepro 500 cards...

Thank you for your thoughts...