We recently had a short dashboard downtime which was determined to be related to our monitoring of the online / offline status of MQTT-connected devices. We've pushed a fix for that today so a similar downtime can't occur for the same reason moving forward.
One of the side effects of this fix is that it will be necessary to re-connect any MQTT devices to Cayenne in order to display accurate online/offline status and to ensure best performance of other Cayenne features. To do this, if you have a microcontroller like an Arduino/ESP or similar device, please power cycle the device to ensure a reconnection. If you have a Linux based device running a Cayenne MQTT client, a reboot isn't necessary, you can simply stop and re-start the client to reconnect.
If you have any questions about this or suspect ongoing MQTT device trouble, please feel free to ask here or make a new thread. Apologies for this inconvenience - it should lead to greater platform stability in the future!