I tried using a exp Orb on a sylestie of mine. The exp Orb was for 5 levels above my sylestie's level and below. But when i tried using the orb, it said "this pet can't earn any more experience!" . what is wrong and how do i fix it?

Which pet is it? It may be that someone has used a philter to stop it from gaining experience.

It's the only sylestie in tab 5 of my stable. It only shows the genetic scanner icon, nothing else .

The nyte in tab 5 is currently at max level (70) - I believe the devs plan to increase the lvl cap to 75 at some point in the future. Any exp given to the pet will count as an overflow, I believe.

Ok, thanks! But how did it get 50,750 exp points once it reached level 70? And the exp orb said pets 75 and below?

The level limit is indeed 70 at the moment. But pets can certainly keep gaining experience after they hit lv70 - Exhibit A.

All of that experience was gained through battle. But I did just try a lv70 exp orb on that pet, and I got the same message. Looks like battle experience can go into infinity, but there's a lock on using exp orbs, to prevent you from wasting the item, I guess.

as Bluedevil stated, level 75 is intended to be an available level (you can see this when looking at the proficiency page), however it has not yet been unlocked, with lv70 being the current level cap.

I do not believe Exp orbs cannot be used on lv70 pets because they are already at lv70, but lv70 pets can still gain exp via missions and battle.

Any additional exp lv70 pets have when the cap is raised is deleted and they will be reset to 0% progress to lv71, regardless of if they were 1% progress or 10000%.

The fact that they continue to gain exp is because it is easier for Krinadon- I have seen what he's said on the matter, but I can only remember the gist of it not the detail.

The reason that the level progress to the next level is reset when the cap is raised is to stop players like me whose pets do have ridiculous% level progress, so our pets don't just spontaneously jump all the way over the next few levels to the new cap when it's raised