1) Make sure you've downloaded the right mods
https://gtm.steamproxy.vip/workshop/filedetails/?id=1125571106
https://gtm.steamproxy.vip/workshop/filedetails/?id=3009221569
https://gtm.steamproxy.vip/sharedfiles/filedetails/?id=3123134909

2) Make sure your launch options are correct.
STEAMMOD=3123134909 STEAMMOD=3009221569 STEAMMOD=1125571106
(Right-click on the game in your library => Properties => General => Launch Options)

3) Unsubscribe and then subscribe to the mod(s).
This will fix the issue if the mod has recently been updated

4) Verify integrity of game files with all mods installed.
(Right-click on the game in your library => Properties => Installed Files => Verify integrity of game files)

5) Delete all game files and verify integrity of game files.
(Address of the File, may look different)
C:\Program Files (x86)\Steam\steamapps\common\Star Wars Empire at War