Since this has been open for a while with no responses, I might as well speak up.
First, there may be a terminology problem. You refer to both “text file” and “librarie (library)”. Normally, those two wouldn’t be considered compatible; i.e., a text file would reside in a directory not a library on an AS/400. Perhaps you are referring to a source physical file or a data physical file that contains only character fields?
Unfortunately, I know nothing about what ‘Arpeggio’ is or does; so I can’t guess whether it would understand a physical file. If it needs to work with text documents and you’re pointing it at a library, then it quite possibly doesn’t list any files because there are no text documents in any library.
But maybe you used the wrong term and you meant ‘directory’ rather than ‘library’ and no text files are shown when you point to the directory. If that’s the case, then it’s almost certain that the userid that your network connection is running under doesn’t have authority to any text files in that directory.