Reports not processing since upgrading to 5.5.0

I just upgraded to 5.5.0 and now all my reports aren’t being updated. I have invalidated all the reports and still no new data is appearing and I see the following when viewing reports for the current day:

It looks like reports for this period have not been processed yet. Do you want to see what’s happening now? Check out the Visits log or choose a different date period until the reports are generated.

This was all working perfectly prior to upgrading (from 5.3.2).

I do wonder if the invalidations / new reports are still being generated … is there a way to see where the report generation is up to?

All help appreciated.