Why can't I combine the solids

[Karol-Or]

I want to combine the rectangular box and the shape, but it returns an error message

[imadHabash]

Hi,

i think that your box didn't set well ... i move it again to match the big shape edge and it's work . see attached CAD file . 

Regards,

[Karol-Or]

You placed it a bit incorrectly, the 2 slots must be equal width and they aren't in your drawing. the box protrudes into one of them, making it narrower.

But now i decided not to use the box and want to move a face and i can't.

The small cyan and big green faces.

By the way, why is the cyan face separate from the green one? i made them, i think, the same.