I realized that I'm having problems with pairing new devices with my QC35 with firmware 1.2.10 . When I hold the power button in the bluetooth position, it does not go in the 'ready to pair' mode. But, everything seems to be ok when I access that mode from the Bose Connect App.
Hi there ! I had a similar problem and it turned out to be a faulty button, it's not a firmware issue , you need to contact your local Bose support and they will replace / repair it as they did with mine! Good luck !