Hi Nezah,
According to the screen shots, the search settings for the given Site Collection is ok. As I understand, the issue is you can’t search for all of the documents in the given library.
Based on my experience, the issue can be caused by the keywords you were using when doing the search. I noticed that you were using the content type name as keyword to search the items, it may not filter all the documents. At this time, I suggest you use any different keywords (For example: The document’s title) to search, and see if you can find any of the document.
If you still can’t search the document with any keywords, please do the following testing to help us narrow down this issue:
1. Please recreate the library in another site collection, download the documents and upload it to that new library, check if you can search for the documents in that library.
2. If there is any other libraries in the given site collection, please try to search documents in those libraries, see if the issue only occur with that given library.
Best Regards,
Evan Zhang
