@acer YES! This is it. I thought I had gone through all GUI menus and options looking for an option like this, however I was not looking at the bottom of the screen (where the status bar is in Maple 2018). I thought all toggles would be at the top of the screen where every other option is...

Thanks very much!

@acer Thanks for the advice. However I believe it is not a GUI issue, it is some property of the document has been set to disallow execution etc. The problem persists even when closing/reopening Maple, and even if I open the same worksheet on another Maple install on a different system