Kanna link skill glitched?

i couldn't figure out how to get the "to next level" button, any help with that?

Just do all the "important quests" in his To Do window, and all the Know How assignments for your level, and it appears.
From level 41 to 49 all it had me do was Ilji's drake killing and one round of Azwan, I think. Then later in the 50's it was just Tot's own tutorials.