Looks like Windows is still seeing your previous 6 core 12 thread processor and not the new 8 core 16 Thread processor.
First do a CMOS CLEAR of your BIOS so that it goes back to factory defaults and again recognizes your new Processor at the same time.
Then go to Windows Search, enter MSCONFIG, it should come up showing System Configuration.
Afterward restart your computer and configure BIOS settings again and see if Windows is showing the correct amount of cores and threads for your new CPU.