[Paul M]

The reason none are being displayed is clear from the whoread table - the newest record in it dates from 17 Aug 2006. Something is stopping the mod from adding records to the database.

Check the plugins and make sure you have the "Display Thread Readers (2)" plugin and it's enabled.

If it is then I would say another plugin connected to the showthread_complete hook is broken and preventing this from running - change the above plugin execution order from 5 to 4, that should mean it gets run first.

If that does mean records start getting added again then you should change it back to 5 and start disabling other plugins on that hook until it starts working - you have then found the broken hook.