Since I'd been having a lot of trouble getting this working, and I assume others will as well, the issue with the 10 second press to reset is the device it's currently paired to cannot be connected to it.
In my case, I have Flic buttons paired with Raspberry Pi devices. To unpair it, I had to turn off the service that was listening for Flic button presses. Once I did that, the button lit up red when clicked. This is the indication I needed so I could reset it. At that point, I was able to pair it to another device the same way as a fresh button.