When I copy a line on the surface by clicking the line, pressing Ctrl, entering a dimension and pressing enter, it doesn’t copy the line for me, so I have to use the guide lines. But if I do the same thing with another line in the same group, it works.
you do have the move tool active?, as control is a modifier of both move and rotation
maybe best to upload the example.
any other cause/solution found for this? I often (and seemingly randomly) the same thing happen: select edge, activate move tool, hit Ctrl for copy, move cursor to set direction, enter distance, hit return… nothing. The copied edge just dissappears. Other times it works just fine…??? Seems to be related to distance input because the workaround is to draw an edge of the distance that I want and then do the same thing but inferencing to the edge, which is annoyingly extra. Am I missing something obvious here?
A week or two ago, a similar problem was reported on this forum. I have seen the issue, rather rarely, with SketchUp Pro 2018. Seems to be a genuine bug in SketchUp. The work-around from @colin was to simply type the distance and press Enter/Return again. That worked for me, when the issue happened to re-occur.
We have worked on this problem, and it hopefully is fixed in the next update.