You need to upgrade your FC to the BETA version of BetaFlight 3.2 in order to make BLHELI_32 passthrough work. You can upgrade Your FC to 3.2, make changes and than downgrade back to stable BetaFlight 3.1.7. You can download pre-release version of BF 3.2 from here: https://betaflight.qmd.cl/
]]>