Using the view drop down greyed out

I just downloaded and enabled the module.

However when i went to the vocabulary page to edit and attach a view, Under "View Usage" i checked the box next to [Use view override] which showed the rest of the option but the drop down select list under "Using the View" is greyed out and will not allow me to change it and it is already assigned to a different view

How do i fix this so the drop down can work and i can chose a different view

Thanks