Thanks for your reply! Are you using TestRail Server or TestRail Cloud? If using server, then a report not generating could be related to the background task not configured properly, and you would just need to be sure you have this configured as per our installation guide:
If you do have the background task configured and other reports are generating properly but large ones aren’t, then this would likely just be a PHP memory limit issue as PHP’s memory limit is quite low by default. I would recommend increasing this in your PHP configuration file and trying the report again to see if it resolves the issue:
With TestRail Server, you would also have the option to build/customize your own report plugin if this is mission critical to your team. While this would take a bit of development work on your end, we do have a guide that can help you in getting started with this if you’re interested in this option:
Hope this helps!