Installed New Matomo Server but doesnt track all

Hi, I installed with success the Matome Server on premise.

I added new WebSite (Based on wordpress installation) to it with success.
On website I installed Piwik plugin and connected the server succesfully.

But this installation doenst track all visits, and when I go to the site dashboard I get an errot on visit resume widget: “Ooops … there was a problem with the request. Maybe the server ran into a temporary problem or maybe you requested a report with too much data. Please try again. If this error occurs repeatedly, contact your Matomo administrator for assistance.”

Thankyou for tips.

Piercarlo