When I started the game again after a long time, I accidentally turned off the feature where it loaded back friends who have the game. How can I make it to where can I see them again?

I dont think there is a button that removes all your friends . your neighbors are gone probably because of the same reason mine are. When zynga sold the game to bvg . bvg only recieved 2 years of accounts . so the accounts that didnt get on for two years before the game changed owners, are gone .

You can unhide all your off line buddies on the top of the buddy list. is that what you mean?