Just putting it here in case someone bumps into it, and is stumped.
I recently changed and got a macbook. I moved from linux and one of the nice features I jumped to mac os were, seeing a misspelled word, right click -> see the suggestion, and correct it.

Problem started appearing when I updated to the new Catalina 10.15.4.

After that update, I started noticing that even though my words were being checked for spelling (showing an underlined squiggly line), when I was right-clicking, I kept receiving a Loading suggestions and nothing appearing as a suggestion.

I tried everything.

Resetting the dictionary, following apples suggestion, nothing seemed to work. In the end I gave up.

Had another fresher look and did the following:

System Preferences > Language & Region:

I removed the “second” preferred language, and restarted my mac.

It worked

I hope this helped!