@simmingonsixam If there isn't a symbolic link in OneDrive's version of Documents, then Sims 4 won't know to look for your user data on D. If you're fine with OneDrive in general and just want to create a working symlink, use this guide:
https://crinrict.com/blog/2020/02/moving-windows-documents-folder-to-external-drive-via-symbolic-link.html
The command would be this:
MKLINK /J “C:\Users\avama\OneDrive\Documents\Electronic Arts” “D:\Electronic Arts”
Or you could add The Sims 4 to the end of each path if you want to link the Sims 4 folder rather than the Electronic Arts folder. Make sure there is no existing folder with the name of the symlink you want to create in the location you'll be creating it—rename the current folder if necessary.
If you'd like to get rid of OneDrive first, here's how:
https://answers.ea.com/t5/PC/CURRENT-ISSUE-Sims-4-saves-user-content-disappearing-PC/m-p/12475370#Remove
Then you'd adjust the first part of the command to reflect the folder Sims 4 started reading with OneDrive out of the picture.