Sometime myQ did not record the door was opened. If you check the status, it said open. However, if you check the history, the door open is not always registered. That make the notification failed.
I also noticed this behavior recently for the last few weeks. My Chamberlain GDO with build-in WiFi and does not need a separate MyQ box and sensors. I cannot blame the battery on the sensor as reported by other posts. I think it is something to do with the Chamberlain server not keeping up with the status reporting. JMO
I am seeing the same issues... I called customer support and they had me disconnect and reconnect the devices. When that did not work they hade me completely remove the hub and reinstall all of the devices and when that did not work he said to do it again. When that did not work he said to keep doing it... I hung up... Tech support SUCKS!!!!