Vitality and Strength materia increase +0

Hi. I have level 30 items like steel cruise that I'm supposed to be able to attach level 1 and 2 materias to them. When I do so, it says that item level is too low to maximize the materia's potential. Then it says it gives +0 increase which is nothing. This only seem to happen with strength materia and vitality. I asked in the game chat but no one seems to go through the same situation. I got all the items that I need; including an armorer lvl 30. Thank you and please help me solve this problem.

Items have stat caps.

They have stat caps? So this happens to me almost with all the items. Even items without a single materia.

Thank you so much. You are right and I had no idea HolyHunter :)