One of the possible reasons for this could be that the Astera Server does not have access to the directory where you are trying to export your file or import it from.
While working with Astera, you must be connected to the server to execute any jobs. Astera client is only used to design and submit jobs to run on the server. If the server is located on another machine, it needs to have access to your files. This requires you to have a shared folder accessible by both client and server machines.
You can also access files from your local directory if the server is installed on the same machine as the client.