Cannot cast fireball lvl 17 + 6 in demon form

POE2 witch
I can cast the fireball lvl 17 in human form (without my weapons) but not when i turn in demon form (17 + 6). the requirements is 164 intel, I have 294. I've remove the support gems. I have 1254 mana (more than enough). I've tried getting my intel to 400, no changes. I did half my level this way no problems and now i can't use it. Lvl 16 works no problem. Is there any other requirements??? Feels like a bug to me. Still no answer.