[Xymon] Acknowledgements Report - No events acked in last 0 minutes

Is the Acknowledgements Report working at the moment? I saw it was a new feature of 4.3.19. We have recently upgraded from Hobbit (2009) to Xymon 4.3.19.

When I click on Acknowledgements report and select today, this week or this month for example, it goes to a blank page and always says :

No events acknowledged in the last 0 minutes.

Any ideas?

thanks