Text widget ability dissapeared & slow to update widgets

Hi,
I’m having quite a bit of trouble at the moment.
I’m upgrading to a new theme and before I done so I tested it all out on a sub domain. Everything works fine on the sub domain which is found at https://news.whatsonthetube.net including the use of widgets.
On the main site https://whatsonthetube.net when going into the widget settings the ability to use the text widget has dissapeared and when making any other changes widget wise especially in the footer they take forever to appear on the site.
I tried to re-install Word Press thinking that might bring it all back and make things run again, but obviously didn’t.
Any help will be appreciated, thank you.