how to fix it?

Thanks for creating the issue.

Do you have logs registered in your Matomo (Piwik) database? If your Matomo tracking code is properly installed, Matomo would record visits in your database. To check if you have logs in your database, go to Matomo > Visitors > Visits log, and select “today” in the calendar. If you see recent visitor information, it means that the visitor tracking is working, but maybe there is a problem with reports archiving.

If you see visits in the Visits Log but not in the reports then please check your archiving works correctly.
-> Please review our doc here: https://matomo.org/docs/setup-auto-archiving/

This should resolve your issue. Please check and if you have any issue let us know or re-open the issue.