problem with dac channels

[Atabua]

Hello everyone, I hope you can help me in some way.

The behavior of the dac channels is very confusing for me, and I would like to know if I miss something or it could be a fault on the board.

it turns out that when I use the dacWrite (25, 0);

I get 2.39v

and dacWrite (25,255);
will result in 0v;

I'm confused, because apart from it works in the opposite way, I don't get the 3.3v that I should get.

Any suggestion?