I tried reactivating the plugin as I thought I’d be able to click remove on the actual widget in the admin screen. But although it reappears in the sidebar menu on the admin screen I can’t click on it to open it up. And the above message still shows on the live site.
I’ve tried deactivating all other plugins in case something was upsetting the vcita widget and that made no difference. I also tried resetting the theme to the default theme and that made no difference either.