Hello,
I have a user who deploys SSIS Packages to the server. I have him run all his Packages as the SQL Server Agent User. The SQL Agent is run as a Domain Service Account so it has access to what is needed. The Package Connects no problem to all our Databases and any open share. However, if we specify a Share that has permissions (which I explicitly granted to the Service Account) the SSIS Package fails stating it cannot open the file. I have logged into a PC with this account and Open the file but it always fails to run with cannot access file (.csv file) when running package from server.