Visual Editor Not Working After Switching to Child Theme

Hello

Yesterday, I decided to use a child theme as I had huge amount of CSS. I moved all the CSS to style.css file and all the functions I had to functions.php file. Zipped and uploaded the theme. Activated it. All good.

Except, the visual editor is not working.

What do I mean by the 'Visual Editor'?
I still use the Classic Editor. While writing a post (Posts > Add New), the classic editor has two tabs. One is 'Visual' and another one is 'Text'. Now, only the 'Text Field' is visible. Visual is disabled. Nothing happens when I click on the Visual tab.

The only change I did was making a child theme and activate it. Absolutely no other changes were made. What gives?

There were similar topics like this here:
https://generatepress.com/forums/topic/visual-editor-in-wordpress-not-working-in-theme/
https://generatepress.com/forums/topic/visual-editor-not-showing/

They didn't help either.

Any help would be much appreciated.