Nothing appears in the Rhino Command Line when the error happens.
One other necessary condition to reproduce the problem: it appears that if I open Rhino 6 and Grasshopper and then close them and open Rhino 7 and grasshopper, the problem does not occur. It only happens if, after a restart in Windows 10, I open Rhino 7 and grasshopper.
I noticed both if your views are top-down. Does the preview exist in the perspective view?
In the GH preview selected objects are moved ever so slightly closer to the camera to avoid them being drawn behind identically placed, unselected previews. If this motion is moving them beyond the clipping depth, they will no longer be drawn. That’s definitely a bug, but should be easy to test by looking at the geometry at an angle.
FYI I triple checked and the only way to reliably fix the issue is to open R6 after a restart, open GH, open the file, close it all, and then open it all in R7.
Workaround : had same propblem, but only on top view, so I took another view where it was showing normally, right click and choose split view (horizneally or vertically) , and the converted the new viewport to top view again and it worked out.