What browser, device, operating system are you using when experiencing this issue?
Here is a link to the list of smilies:
You could always copy and paste them in if you can't get the formatting button to work.
I think it's my system. If the emoticon button does not show up I have to log out and log back in. Usually, they show up. weird
Especially if you're using a phone or small tablet.
Browser positioning problems can be erratic. Try using a different browser (if available) to see if the results are similar. If it keeps happening, try posting screen captures of when it isn't, and when it is, working so people can get a better idea of what might be happening.
I haven't had that issue so I can't offer anything very specific.