What to do when downloading a file by Appeon File Server, though the files exists under the specified directory and the physical directory in AppeonFileService.log is correct, the download fails with no indicated error?

That might be caused by that the cache of Appeon File Server doesn’t match the actual file. For example, if you manually modify or override a file directly in Appeon File Server machine instead of uploading a new file by Appeon File Server, then this error would occur.

Please go to Appeon File Server and find the directory of that file, then delete the appeon.lst under that directory (it’s the cache file of Appeon File Server), and then restart IIS.