I'm sorry you were having this problem. (Hopefully it has resolved itself since you posted this.) I don't know what could have been causing it. Perhaps it has something to do with whatever type of devise you're using to access PC? I use an old (by computer standards) laptop computer & have not been having problems for the most part.

One problem I have encountered, on occasion, is when I would click on the "More" icon (at the bottom of the smilies box) sometimes the box containing all of the additional emojis wouldn't come up. That has occurred a few times recently, but not over the course of the last 2 of 3 days at least that I can recall. What I have found, here on PC, is that whenever little problems of this sort occur, it seems like after a while they simply disappear on their own & I never know why they occurred. Hopefully the problem you've had with the emojis has disappeared on its own too.