Player sees only grey on the VTT

Hi, I'm very new to Roll20, and I'm trying to research what I can on my own. I'm stumped with a VTT-visibility issue, however. A friend is trying to help me test, but we're at a dead end. I'm hoping someone here can help me troubleshoot.  I have added a background image to the map layer, and I have it aligned with the VTT grid well enough. I have Fog of War enabled, with a portion of the map revealed. The red flag in the pages banner indicates my players should see that page. A player is assigned to one of the characters. and I have added that character's token to the visible area on the map. When I switch to the player view, I see what I expect players to see (a partially-exposed map, with everything else covered in black). My friend, however, sees only grey in the VTT. I'm guessing I've configured something incorrectly, but I can't figure out what that might be. Can you help? Thanks kindly, Joseph

Have him check to make sure that his browser is Chrome or Firefox, and that it allows javascript to run on roll20.net.

I am having the same issue right now.  I'm a GM, and all my maps are missing right now....they just load as a grey screen.  No maps, tokens, nothing.

I just deleted my roll20 cookies in FF and restarted the browser; this fixed it.

I tested with another friend, and he's seeing the map as I would expect. I'll work with my other friend to troubleshoot on his end.

Using firefox enabled him to see and interact with the map. We're having some audio issues with him, but I'll research those outside of this thread. Cheers.