Lost save game
You mention not being able to find your families in-game. Do you still have your saved games in your Sims 4\saves folder? [C:\Users\Username\Documents\Electronic Arts\The Sims 4\saves]
If you're missing your saved games, check that they are still in your Sims 4 folder. You can do this by searching your computer for the Sims 4. Do this by clicking the Start button and in the Search bar type Sims 4 and follow the path it gives you.
Default path for the Sims 4 user files is - C:\Users\Username\Documents\Electronic Arts\The Sims 4\savesIf you're not finding the files there, the computer may have created a new folder for you in the Electronic Arts folder. Or moved the files to OneDrive.
OneDrive and Sims 4 don't work well together. The game saves need to be in the Documents\Electronic Arts\ The Sims 4 folder for the game to recognize any of the saves. Any save files can be safely moved to the Sims 4\saves folder
It is best to turn off or disable One Drive for Sims 4. So this mixup doesn't happen again.
How To: Turn off, disable, or uninstall OneDrive
https://support.office.com/en-us/article/turn-off-disable-or-uninstall-onedrive-f32a17ce-3336-40fe-9c38-6efb09f944b0
