SSIS package not copying files when run from SQL Server Agent

I have a simple SSIS package that copies files from one directory to another and then deletes the source file. It works fine when run from Visual Studio. Although when I add the package to the SSIS catalog and schedule it via a SQL Server Agent job the files do not get copied over. The job history is showing no authentication errors, so I have no idea what the issue is. Any advice would be appreciated