Token Symbols Not Working

Hello,  Currently, I have two games in Roll20, both of which are running a D&D 5e campaign. I've been running them both for over a year now with little in the ways of issues. However, recently, one of my games has run into an issue. When I place a token down on a map and click the symbol button, only the first few colored dots and the X symbol appear. All of the black and white symbols such as the skull and lightning bolt look like they are about to load in, and then they don't. I was wondering if anyone knew what causes this issue and what can be done to fix it.

You might want to check to be sure what marker sets are active for that game on the details/launch page, and maybe try removing/adding the set(s) you want to use. I haven't had an issue with markers showing up so far.

Thanks for the help Kraynic. I somehow accidentally removed them from the game. They are now back.