Hi Fredrik, did you use the nothing X app? If yes, did you use it to pair your devices together? The app (for no obvious reason) will need you to turn on your phone's location (and the bluetooth of course) in order to proceed to the pairing process. Once it's done, it'll ask you to leave the case open with the earphones still inside then keep the button pressed until the light blinks.
I'm pretty sure you've already been through all this but it was'nt mentionned on your message. I had trouble to pair it once, my right earphone was'nt showing through the app and I tried to forget it and pair it again using the app. I managed to get it working by forgetting it through the bluetooth menu of my phone after forgetting it on the app, then restart the pairing process.
Sorry for my english, not my native language. Hope it helped.