When a player travels long distance (over about 200 blocks) before their pets can teleport, and the pets are in entity ticking chunks and in the same dimension, the pets often becomes invisible when they teleport to the player.

Key Points:

1. Invisible Pets: You won't see them or their hitbox with F3+B, and you can't interact with them (no leading, feeding, sitting, damaging, or throwing a fishing rod on them).

1. Reloading Needed: This issue stays until the pet is "reloaded." You can switch dimensions, restart the world, or move far away without them following.

1. Funtions Still Active:

• • You can still hear them.
  • They still follow or teleport to the player.
  • They can update pressure plates, tripwires, chests, etc.
  • They can still ride in boats, taking up one seat.
  • They can still breed if already fed beforehand.
  • Mobs like creepers are still scared of them.
  • They can be damaged or killed by mobs, explosions, or lava.

The attached image shows creepers avoiding an invisible cat that's in the back seat of the boat.