This guide will let you know how to fix the “NO OPPONENTS FOUND” error in FIFA 21.
First, you have to boot up your game and then go to the Customize tab. After that, go to Online settings and select Match-Making Options.
Under matchmaking, the approximate location of matchmaking is set to yes by default, you have to set it to NO. After that, save the settings, then find the opponents, and your error will be fixed.