Hi Ken, thanks for your reply
No, when I selected my menu & menu item from the ‘menu settings’ and hit save, the page reloads with that error and both drop downs say ‘select menu’ and ‘select menu item’ again.
In the front end, I can see the menu and parent item but none of the cpt links are being generated.
Having said that, I have actually created the required menu without the use of a plugin now, but I thought perhaps someone else may be having a similar issue to me.
Thanks
Nat