Could not read - because it is a not a file

Error:

I have a process flow that is failing. There is an FTP trigger which seems to be working - the event is kicked off when it fires after the file is placed on the FTP server. But then the process is aborted, and in the diagnostic the error in the Source FTP says

"Error initializing activity FtpSource:TestFTPSource[Could not read from ""sftp://test/file.txt"" because it is a not a file.]"

Cause:

1) The file being picked up is not valid

2) The FTP trigger and FTP source are pointing to different FTP servers

Solution:

1)  Validate the source file

2) Set the FTP trigger and FTP source to point to the same FTP server