No Reporting Information - "No Record Found"

The bug is fixed in 17.5 MR8. Please upgrade and let us know if the issue reoccurs. 

https://community.sophos.com/products/xg-firewall/b/blog/posts/sfos-17-5-mr8-released

NC-46780 [Logging Framework] Reports not being generated when Email Notification feature is enabled

A reboot would also fix it temporarily (or restarting the garner service). 

The bug is fixed in 17.5 MR8. Please upgrade and let us know if the issue reoccurs. 

https://community.sophos.com/products/xg-firewall/b/blog/posts/sfos-17-5-mr8-released

NC-46780 [Logging Framework] Reports not being generated when Email Notification feature is enabled

A reboot would also fix it temporarily (or restarting the garner service). 

I updated a few minutes ago and now I'm seeing a little data being reported. Am I correct in thinking this bug didn't just prevent the report from generating but actually prevented any data from being recorded during the past week?

That's correct, it would have hung the service which passes the data along to the DB.