Help can't flash TWRP in S-ON state?

Just got my HTC 10 and I'm trying to root and install twrp. I have the unlocked version from HTC. I've unlocked the bootloader and installed all drivers. Everytimei try to flash twrpvia fastboot I get an error saying cannot write to this partition in s-on state. See screenshot. If anyone can help it will be greatly appreciated. I have the unlocked version straight from HTC. TIA

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