It seems that your connection monitor window was left open. The connection monitor runs in the background and continues to track uptime/downtime, but it doesn't refresh the window while it remains open.
In your screenshot, the last recorded data point is from May 30, and the uptime since then is 105 hours, which corresponds to approximately four additional days, bringing it to the current date. By reopening the Connection Monitor, the missing ping records for May 31, and June 1-3 should be displayed.
There is no need to keep either the Speed Meter or the Connection Monitor window open continuously. Both speed testing and connection monitoring will continue to operate in the background.
To prevent this confusion in the future, we will update NetWorx application so that the Connection Monitor window refreshes every hour.