[galaxy-user] Cannot upload file to data library

Hi all, I created an account in our local Galaxy instance and it's a non-admin one. I have set up Galaxy (I have an account that's an admin) so that my user account can upload files to a data library. But when I tried doing it, I got the following error: The directory <some folder here> contains no valid files. I checked the path to the folder and it was correct. I also checked if I had really placed the FASTQ file inside the folder and I found the file there. Why is Galaxy telling me that there is no valid file within the folder when there's a file present within the directory? Thank you in advance for any help! CL