I added the wordpress plugin to one of my sites last week and I am still seeing this message.
No data yet
To see reports, you need to install our container on your site or app and start collecting data.
The debugger sees the data when I test with that.
I have installed Piwik Pro on another site the same way and that one worked fine.
Incidentally, this second site also has an issue with Google Search Console verification - could this be related?