Moodle reports usually contains a lot of data and tends to be heavy on the server. Depending on the server configuration you have, generating reports might take awhile before succeeding or might return an error message at the end.
Here are basic troubleshooting steps you can follow, if you encounter an error:
- Try to generate report during off-peak hours. With this, your server resources can focus on generating your reports.
- Error messages can contain specific detail to point out the issue you have, be sure to read carefully and fix the problem at the root.
- Contact you Site Administrator or Server Administrator to report the issue. They should modify some configuration on your server and increase necessary settings.