Thanks for this guide! I had given up getting my buttons to pair and put them on the shelf for a while. I brought them back out today and was able to follow this guide to get them paired and updated.
One thing I noticed, and you mention it, but I wanted to make it even more clear - you need fresh/new batteries in these things to get them to work. The batteries mine came with, and even the first batch I ordered from Amazon did not have enough voltage to get the stock firmware to work predictably. When I put new (fresh) batteries into the buttons, then everything was good! Hopefully one of these firmware updates makes it more reliable as the battery wears down.