Hello
The birthday set mod may have become broken by a recent patch. Try removing the mod, deleting the cache files,
https://sims4.crinrict.com/en/2014/09/delete-cache-files/
Then loading the game and see if the issue with your sim remains.
If it does remain, then exit the game, and try moving your whole mods folder to the desktop. Then start the game and test to see if that helps the issues.
You could also try recovering an earlier version of your current save game to play, that is before the issues occurred. To do that , go to the main screen of sims 4, and click on the " load game " button.Click on your save game file picture. Then click on the " recover game " button down the right hand side bottom of the screen,. Press on an earlier version of the save game from the menu that pops up. Then load that save game version.
