we have seen that piwik did not track any visits since our update to 2.4.0. After a bit of confusing and debugging, we have found, that the tracking code failed to insert data in piwik_log_visit for the coloumn config_os_version, as it did not exist. We have found out that this belongs to the DeviceDetection, which was disabled on our system.
To us, it looks like there is a bug that either DeviceDetection needs to be disabled or the respective coloumns should not be addressed in the query. Can you confirm that? Right now, the query is running to update the table, which could take a while though (1.7GB ). I will post here if that fixes the problem, but would be happy about a response anyway.
Edit: I can now confirm that it is fixed after enabling the DeviceDetector module. I have filed a bug for this: Core piwik uses coloums in log_visit that are not available when DeviceDetector is not installed · Issue #5902 · matomo-org/matomo · GitHub