Gallery thumbnails are all X'ed out

@lsnishi  ♥

@sterobeuk 

@mooncake 

@Peapod79 

Have a look here. All known solutions to problems with the Gallery are gathered there.

https://answers.ea.com/t5/General-Discussion-Feedback/READ-FIRST-Status-of-the-Gallery-SCHEDULED-MAINTENANCE/td-p/9514109/jump-to/first-unread-message

Personally, I recommend that you start repairs by resetting the game folder.

Go to Documents/ElectronicArts - inside will be The Sims4 folder
The path to The Sims 4 folder in Win 10
This computer> drive C> Users> computer name or your name> Documents> Electronic Arts> The Sims 4
Step 1. Move The Sims4 folder to the desktop
Step 2. Fix the game in Origin
Origin/ My games library - right-click on TS4 - option "Repair game"
You have to wait until Origin will fix all packs, not only the base game.
Step 3. Turn on the game - a new game folder will be created and you will have two - one old on the desktop and one new
Step 4. Check if you still have this problem in the newly created game folder. Start a new game and check if Gallery is working properly
If the problem disappeared
Step 5. Delete in the new game folder following folders:
"saves" and Tray.
Step 6. Go to "The Sims 4" old folder and copy - your "saves " folder.
Step. 7. Paste this folder in a newly created game folder.

Step 8. Do the same with the Tray folder and TrayDeleteItems file if you have this file in the old folder on the desktop
Step 9. If you don't use mods and cc skip this step but if you have them, check if there are newly updated version mods you are using.
Then copy and paste your mods and CC from the old mods folder to the new one. First copy the scripts mods every time checking if the game is working properly. If you have a lot of CC try the 50/50 method ( divide your CC into smaller batches for example 50 pieces in one subfolder and check these subfolders one by one)
Step. 10. Launch the game and check if this problem disappeared in your old save
The last step - delete The Sims4 folder from the desktop
Your saves and library will be not changed or damaged

I don't work for EA