No data visible after Update from Matomo 3 to Matomo 4.1.1

Hi there, i’m new. We updated our Matomo from 3.X to 4.1.1. But now there are NO former data visible.
And it seems, that no data is collected.

I found this error:

Can someone help?


net::ERR_CERT_COMMON_NAME_INVALID is Chrome telling you that the common name of your SSL certificate for is invalid and therefore the browser refuses to connect to it.

Maybe check your HTTPS setup.

Thanks. The error message is gone now. But the data is still not there.
After increasing the time period a little, I noticed that parts of the data seem to be displayed, but only until April 2020. After that, nothing more.

Matomo seems to track now. But the data-loss from april to december ist still there…