When you wish to download an entire flow as one ZIP-file, it can take quite a long time from the point where you have clicked "Download as ZIP" till the file is ready for download. Especially on flows that include many large hand-ins - e.g. video material as extra material. The generation of a ZIP-file can take 20-30 minutes in these cases. The reason for this is that the files are being compressed and structured in the ZIP-file. The amount of time it takes is dependent on the magnitude of data.
In flows with big media files and few participants, it often pays to download the files one at a time.
For these reasons, we always recommend patience when waiting for the ZIP-file to generate. However, if the generation time exceeds a reasonable time limit, the process might have failed at some point - e.g. in border situations this can be due to a misalignment between participants and their cover sheets. In these situations, we suggest trying to reset ZIP-file generation process by reordering the export. If the problem persists, we suggest that you contact your licence administrator.