As mentioned in FAQs, the TMC6100 needs to be enabled and there is mention in FAQ of special firmware to correctly pair the TMC4671 to TMC6100 with a link https://www.trinamic.com/support/eval-kits/details/tmc4671-tmc6100-bob/#downloads-4
Unfortunately this only takes me to the product page. My IDE is 3.9.0
Thanks,
Tim.