I read earlier threads regarding this scenario and tried all the recommendations. None worked. My edges are showing, played around with the field of view, checked the expert dimensions settings (nothing used), and only the dimension lines and tick marks show. When I double click the dims the text appears as selected. But as soon as I release the selection they disappear! I just upgraded to 2021 so is it a glitch in the matrix?
Perhaps you could share the .skp file so we can see what you are working with?