Just to ensure we are talking about the same: in such cases normally there is no need to update Wind 10 system itself, what you have to update are the fastboot driver on your win 10. So did you follow the steps in the topic linked above? Also, the update on win 10 has no influence on the LED of the FP2 (if I remember correct, the LED sometimes does not blink blue and you can still be in fastboot mode).
Btw. why do you try install TWRP to flash FPOS Android 10? It will be overwritten with FPOS recovery when you flash it.