UI button doesn't work when it's above my game board

Hello, everyone.
For an end of year project, I have to use my teacher’s code to create the numerical variant of a board game. For the moment, I’m replacing some buttons but my problem comes when I want to click on them.
When it is visually above the board, the button doesn’t work. I can’t figure out where the problem comes from. I try to use a “!EventSystem.current.IsPointerOverGameObject()” but nothing works.

Would you know where the problem could come from?
Thank you very much everyone.

PS: Sorry for my bad English, I’m French and I use a translator.

PS2: The first button only works if I click it but without being above the tray.

you try use OnClick() method in Button Component ?