A successful upgrade doesn’t always mean the reporting data is being processed correctly. Since the problem started immediately after upgrading from Matomo 4.4.1 to 5.11.1, there are a few things I’d check first:
Verify whether new visits are actually being tracked by opening Visitors → Real-time and visiting your site yourself.
Check whether the archive reports are being generated. If you’re using cron archiving, make sure the archiving job is still running successfully after the upgrade.
Review Administration → System → Diagnostics (or the Matomo logs) for any database or archiving errors that may not appear in the basic System Check.
Clear the Matomo cache and, if available, trigger Invalidate archived reports so Matomo rebuilds them.
Since you’re upgrading across several major versions, it’s also worth running any pending database migrations again to ensure nothing was skipped.
If those don’t reveal the issue, it would help if you could share:
Do Real-time Visitors show new visits?
Are all websites affected or just one?
Is the visit count missing for only new data, or has all historical data disappeared as well?
Are you using browser archiving or a cron job for archiving?
Those details should make it much easier to identify whether this is a tracking, archiving, or database migration issue.
Verify whether new visits are actually being tracked by opening Visitors → Real-time and visiting your site yourself.
No, they don’t, it’s all blocked at 14th June 2026. Nothing since.
Review Administration → System → Diagnostics (or the Matomo logs) for any database or archiving errors that may not appear in the basic System Check.
Yes, tons of errors in the logs (see my previous message).
No issue in the diagnosis though.
Are all websites affected or just one?
All.
Is the visit count missing for only new data, or has all historical data disappeared as well?
I can see former data.
Are you using browser archiving or a cron job for archiving?
Browser cache.
The log that I posted before show an issue in the database format, probably a failed update? So no data seems to be recorded because all MySQL requests fail.