Perhaps has something to do with the view but I cannot get the measurement guidelines to stick. They appear but when I hit enter, they disappear. Was not having this problem earlier today.
Go View menu and tick Guides.
@Box is correct. As you move the cursor to place a new Guide, SketchUp displays a “ghost” showing where the new Guide will go. But when you click to place an actual Guide, it is invisible unless View->Guides is checked.
Sure enough that was it. When I reopened the drawing “view guidelines” was turned off. Thanks