Batteries / Battery Holders
If a Smart Vent is offline or going offline intermittently, it's most likely that the battery holders are not tightened or aligned properly. This can produce a gap where the batteries are not secure - or the pin connector on the bottom battery holder is not fully connected to the Smart Vent. Try tightening the battery holders.
Also, try replacing batteries with fresh, new batteries. If you do replace batteries, wait 60 seconds before replacing them.
Signal Range
Another reason a Smart Vent is offline or goes offline intermittently is its signal range to a Gateway Puck. All Smart Vents need to communicate with a Gateway Puck using RF (radio frequency) signals.
Check statistics to see if the Smart Vent is in good signal range of a Gateway Puck. If the signal is low, try moving a Gateway Puck to a more central location - or closer to the offline device. You can also try converting the nearest Sensor Puck to a Gateway Puck, or adding an additional Gateway Puck to facilitate signal strength.
Gateway Puck Offline
Does the Gateway Puck WiFi icon show good signal strength? If not, move it closer to WiFi to improve WiFi signal strength, or check out this article to troubleshoot the Gateway Puck WiFi Connection. The Gateway Puck may be having trouble communicating with the Flair app.
Moved Gateway Puck
If you've moved a Gateway Puck, this can affect its RF signal range to Smart Vents and Sensor Pucks. Try moving it back to its original position.
Re-Link Device
You can reset a Smart Vent's connection to Flair by removing the batteries, waiting 60 seconds, and then replacing the batteries. Then enable Setup Mode to discover and re-link these devices.