Felicias2000 You've probably tried this but just to be sure. If you are playing on a computer, have you tried a folder reset? To do that, just rename the "The Sims 4" folder or move it elsewhere on your computer. Then start a new game, which will create a new "The Sims 4" folder. After making and placing the mandatory sim, save while on the lot then exit to the world selection screen and check to see if Chestnut Ridge is there and accessible. If it is, then quit. Go back to your original user folder and copy the saves and tray folders to the new user folder letting it overwrite what is there. Start the game again using the Load menu. Then check the world screen again to see if Chestnut Ridge is there and if it is accessible. If it is, you should be good to go. If it isn't and/or it is but you can't access any of the lots, then your save is most likely corrupted, and you'll need to abandon it and start a new one. You can probably save any custom lots and your sims by saving them to your library. You can install them in a new save from your Library with this proviso. Your mods folder needs to be in the new user folder before you do that, so you don't have to edit the sims and lots later to put it back. So, move your mods folder into the new user folder before doing that.
And lastly, if you encounter the same problem in the new save after moving your mods folder, then you most likely have something in the folder that is causing the problem. If so, then you'll need to find and remove it so the game will run correctly.
Hope this helps.