I just wanted to leave this comment somewhere because pairing Vive Trackers can be a nightmare.
I had lots of problem pairing a single tracker on a specific PC and headset (I have several PC+Vive setups, and the tracker would pair just fine on all of them, except one).
This procedure allowed me to pair the tracker:
1. I unpaired all the devices using the instructions above (I cannot be sure if this was necessary or not. Maybe steps 2 and 3 would be enough).
2. I connected the Tracker via USB to the PC. This way, the tracker appears on SteamVR's detected devices.
3. I then disconnected the USB cable from the tracker, and immediately after, I right-clicked on the tracker icon and selected "Pair Tracker"
And boom, it paired. I'm currently pairing the tracker with the headset, but its possible that this trick also works with the dongle.
Hope this helps someone.
