For some reason, my main won't level up :<

I was trying to level up my main since I reached level 54 so I started fighting stronger mobs like around 57-60 and when I looked at my exp bar it wasn't rising for some reason so I went for higher leveled mobs like 60-77 but still it wasn't rising does it have a cap? Or am I just doing something wrong? I'm new to the game so I donno

 

It might be because mobs base exp is too low and I usually use boss around my level for leveling. Theres helpful website called coryn where we can find lot of stuff including boss exp.

Also our current level cap is,

Spoiler: Level Cap

270

 

Thank you so much qwq