Not being able to add widgets

Have you tried deactivating your plugins and switching to the default theme to try to identify what may be causing that? If doing that fixes it, reverse the steps one by one to find the troublesome one.

Did you try enabling accessibility mode in screen options?

@wpyogi,
Sorry, it was almost a cross post.

@krishna – I cannot access screen options so will try WPyogi’s way.

Thanks ??

Sorted everyone!

The cause was the plugin ‘WordPress captcha contact form with frontend TinyMCE editor’

Cool!

@krishna – no problem :)!