When you wish to download an entire flow as one ZIP-file, it can take quite a long time from the point when you have clicked "Download as ZIP" till the file is ready for download. Especially on flows that include many large filesize hand-ins - e.g. video material as extra material. At times the generation of a ZIP-file can take between 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 mediafiles and few participants it can often pay off to download the files one at a time.
For these reasons we always suggest 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 in the generation - e.g. in border situations this can be due to a misalignment between participants and their cover sheets. In these situations the we suggest trying to reset ZIP-file generation process by reordering the export. If the problem persists, we suggest that you contact your license administrator.