Custom Symbology in Attachment Viewer not working

[MarisaKordecki]

I uploaded PNG icons to use as custom icons for my layer.

I have no problems with them in my web viewer and they work in another configurable web app (Crowdsource Reporter). 

However, in my Attachment Viewer app the icons do not load. Is this a specific Attachment Viewer issue? Is there a work around? 

Thanks, 
Marisa