I am currently running Descent into Avernus and 3 of my players cannot see the map when I drag their token from the CT to the maps. I have checked and LOS is turned on and the walls are all set up correctly. I'm not sure if its a problem with their characters they made or something else entirely. I'm also fairly new to FGU and have looked into some tutorials and videos. If you have any advice thank you very much!
My dude, check the new lighting option on the map.
The new update added lighting and I ran into the same issue in my Starfinder campaign. The lighting was enabled on the map and only the players with Dark Vision could see anything on the map. I disabled the lighting option off and all the players were able to see everything again. It's cool but I didn't have time to prep the players before the session to let them know about the new lighting stuff.
Click the Lock icon at the top right of the map/image window and disable it there in the menu.
You might want to check this post by Zaccheus and watch videos eighteen, nineteen, twenty and twenty-one to see how to make use of the lighting feature and give lights, torches, candles, or visions to the characters.