Solution to function WP_List_Table::get_columns() must be over-ridden in a sub-class
The Gravity forms are showing weird errors with the latest WP update. The error is as follows:
function WP_List_Table::get_columns() must be over-ridden in a sub-class.
Due to this error the customisation of confirmation and that of the notifications have completely stopped. If you already have created some confirmation message and/or the email notification for your created form, then you cannot change it right now.
For this there is one possible solution suggested by Adam Czajczyk, which you will get here.
Try it it may help you clear up your Gravity form confirmation and notification problems.