If the drawing only show x and y when open a new drawing, it only tell that you are now in 2D mode, but the way you explaine it, the workplane it is not on the same workplane like the objects you try to move, whatever that workplane migth be, so then you can use worplane by entety and select that object, and then moving the object, and there will be no warnings.
Because like it is now, everything is not on the same workplane, 2D or not 2D
Maybe you should attach/ upload an example, then it is more likely sombody will tell you what causes your issue.
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