Bow Skills gone by using a new Bow

Hi, i dont know is it a bug or something in the game-mechanic that i dont understand.I use a bow and found a better one. I equipped it, but most of my skills that i used are gone. When i equipped the old one, i can use all skills again. If i want to add in the skillbar with the new one, then the skills are not there. Both types are bow´s.

Anyone can help?

Did your old bow grant stats (Str, Dex, Int)?

If it does, you may not be meeting the requirements for your skills after removing it.