Searching in the Files App Doesn’t Work!!

I have a large number of documents in the Files app on my iPad. And when i search within the Files app for a particular document by typing in keywords of the document’s name, the only result shown is just “no results”, even if I can plainly see the doc in the file. I’ve shut and reopened Files and restarted the iPad several times, no change. Besides, I actually noticed this bug quite long ago and my iPad has gone through several updates, but the problem still persists, and that why I wish you to fix it because it really causes much inconvenience for those who use their iPad as their major learning tool and store a great number of documents in it.

Thanks!