Try creating the dimension by selecting the endpoints rather than edges. Otherwise you can try converting the entity to sketch and then dimensioning.
Otherwise you may want to attached your model for further review.
Typically you would fully dimension the part and then specify any critical features/dimensions for your first article inspection.
I occasionally get that same message when trying to dimension. My usual practice is to insert some sketch geometry (line, arc, etc) in the drawing view, fully defined with relations to the model edges, dimension to the sketch lines, and then move the sketch lines into a Layer that's turned off so they don't show.
When it happens to me I close and safe the drawing. Then reopen it most times that works. But sometimes I have to shut down Solidworks and restart. Using 2018 sp3. Does not happen a lot Maybe once a month if that.