It doesn't really matter whether your airlock bubbles or not, that's not a good gauge of fermentation, there's enough normal reason why airlockc don't blip to make it a faulty gauge.
(Your hydrometer is the only true way to gauge.) But having said that the fact that you have some bubbles means something IS happening under the hood.
But as it says in the sticky at the top of this section, "fermentation can take 72 hours to begin." There's still nothing to worry about.
You right near the bottom of the temp range for this yeast so they are going to be more sluggish than if it were slightly warmer. you may want to consider warming it a bit, or simply moving it to a slightly warmer space.
After you hit the 72 hour mark, you may want to take a hydro reading and see what's going on, but more than likely when you open the bucket you will see a nice krausen there, or the signs of one starting and you'll be relieved.
Just remember, fermentation is not always "dynamic," just because you don't SEE anything happening, doesn't mean that any-thing's wrong,, and also doesn't mean that the yeast are still not working diligently away, doing what they've been doing for over 4,000 years.