Neither "Recent files", "Recent documents" or "Insert file" will work despite I reinstalled LibreOffice two times. Why?
What exactly is your question?
Are you looking for Files you previously edited?
Are you trying to insert something into a file/document?
Please edit your question and question description to get a meaningful answer.
Recent files and recent documents will only show files that have been worked on in LibreOffice since it was last installed. The reinstallation will erase the lists of recent files and documents.
For Insert File, are you referring to Insert Section where the contents can be obtained from another file? The only immediate thought is that you can’t insert a section unless there is an open document to insert it into.