Why is this question grayed out?
I de-selected the follow star in the tag pop-up:
only to realize that the tag was removed from my favorite list:
So I re-selected the tag again. What did I do?
You must have added one of the tags to your ignore list instead of your favourites list.
The easy way to check is to hover over the tag again. If the star is red then you've added it to your ignored list.
In that case just click it again twice to bring it back to yellow (favourite). If not, then I don't know what's going on.