there might be a couple of areas where the wild pokémon are invisible. it's a recurring bug that comes and goes.
if you're not in such an area, stay closer to your pokémon - they can only protect you if they're nearby. try using right-click movement to send your pokémon into the grass ahead of you (select a pokémon for right-clicking by pressing the number key on your keyboard corresponding to the team slot they're in).
if you're not in such an area, stay closer to your pokémon - they can only protect you if they're nearby. try using right-click movement to send your pokémon into the grass ahead of you (select a pokémon for right-clicking by pressing the number key on your keyboard corresponding to the team slot they're in).