Can you please add a small video (on WeTransfer/Youtube/Dropbox) and post a link here so that it can be looked into?
We have tried to reproduce it but unable to do it.
Also, please try once after clearing your cache and preferences. forums.adobe.com/thread/526990
I have a similar issue happening with 14.0.1.
The 'Change' button, when attempting to find and replace text, is greyed out. 'Change all' isn't tho - but it's not what I need to do.
We were able to reproduce the issue and it is currently under investigation.
InDesign TeamAnonymous commented
I'm now experiencing this issue in the latest update 14.0.1!
The fix for this issue is now available in the latest update 14.0.2 of InDesign 2019.
If you are unable to see the update notification yet, open the menu (three dots) from the top-right of Creative Cloud desktop application and click on ‘Check For App Updates’.
Once the update button is shown against InDesign, click on the button to update to Id 14.0.2.
If you face any problems with the new update, do let us know in the comments.