Add a translation for new post or page

I have three different languages, English, Simplified Chinese and Traditional Chinese, on my website but in the middle of the implementation I have disabled the Simplified Chinese and enabled it back afterwards. The “add a translation in Traditional Chinese” or “add a translation in Simplified Chinese” has become very weird.

After pressing the plus button to add a translation or edit existing translation for the post or page, it will link to the page builder for 404 page and not able to create a translation page for my posts or pages. All my posts and pages have the same problem and I have no idea how to solve it. Please help 😢.

Thanks!