Ok, I had almost the same issue here, tried a mess of stuff 'til I went to the stupid-check and voila.. there was my problem.
It was without mistake a classic case of PEBCAK (Problem Exists Between Chair And Keyboard), which also reminded me never to toggle on something after 1 am in the morning.
Brief description of my problem: I was updating and adding new stuff to my obs layouts, and for some reasons I could hear the sound of my video emotes but could not see them. Even by copying the alert url on a blank page, it wouldn'ìt show. Fun thing is that all other pages displayed the alerts properly, just this one not.
Today I re-re-re-checked all and noticed a little something which made me feel an idiot (much more than I am or usually feel): when I started to stream and built my pages, I decided to separate my layouts into multiple ones, so that I could display some things instead of others according to the page/mood/content. Simply put, I had copied the wrong layout on the page. Once I corrected that little snafu, everything worked just as it was supposed to be. So to prevent anyone else from sobbing on the keyboard for your own bad attention, double check that the page you want something to be displayed into has all the needed layers.
Have fun streaming everyone, hope this helped! =)
