Need a fix for “no results” after searching Files App

My Files App (the one by Apple) shows Adobe Acrobat as a location I can access through the Files App.

Yet when I run a search through the Files App for documents I know are in Acrobat, it returns “no results”.

I have made sure Acrobat (just and example, happens to other apps too) is active under Siri & Search in Settings, but it made no difference.

How do I get Files to search more thoroughly and return results?

I don’t see how it can be useful with this function missing.

TIA

Francois