Player map grey

I'm brand new to FGU and I'm sure this is just a silly error on my part. I've uploaded a couple of maps which I can see and manipulate as the DM. I have a second version of FGU running as a player. If I share the map from the DM side my player side gets the map frame, grid, pins, and any character added, but the map image is missing. I'm just seeing a grey background. What do I need to do to enable the player to see the map?

If LOS is enabled (it is by default) then the GM needs to add a PC token to the map from the Combat Tracker, and then player need to select/activate that token on the map for visibility to be activated.

If a mask has been added to the map, the GM needs to remove a portion of it.

Screen shots and ruleset info always help us help you :)

Here are screen shots of both the DM and Player sides

Attachment 38412
Attachment 38413

I'm running 5E.
I have a character added from the DM side - from the combat tracker
I have selected the character from the Player side
I believe I've toggled LOS on and off and checked after both
I've tried multiple maps both JPG and PNG (the one on the screen shot is a PNG)

Thank you for helping.

How are you joining the second instance if FGU to the first? Try also in a new campaign without extensions. Also how big are the maps Size and resolution (you should only use .jpg files for maps).

I have the second version logging in with the Join Campaign option. I will set up a new campaign and test.

5E rule set
I started a new campaign (no extensions)
I imported a 150 kb - 773 × 1034 jpeg - by dragging it from Assets
I added a grid and a character from the Combat Tracker

I started the player screen with the Join Campaign option.
On the player screen I still see the character token and the grid - but no map.

To the best of my knowledge there is no masking
To the best of my knowledge LOS is disabled

Campaign name: Dave Test
Map image name: dnd_map__the_sunken_city_by_stormcrow135_dv4xxg-pre (1)

Running Windows 10

DM screen shot Attachment 38417
Player screen shot Attachment 38418

Once again I greatly appreciate the help

If your first and second instance are on the same computer then the first instance should be a LAN game and the second instance should use localhost in the join by box.

If your second instance is on a second computer on the same LAN your first instance should be a LAN game and your second instance should use the local IP address of the host computer.

This is what I meant by how are you joining and I should have made that clearer.