This alert tells you that a battery-powered Puck 2 in your home has insufficient battery voltage to complete a needed Firmware update. Flair tried to send that Puck a firmware update, saw that its battery level was too low to finish safely, and stopped the update instead of starting it.
You'll see this as an email with the subject "Flair Firmware Update Blocked for [your home] - Critical Battery", or as a notification titled "Flair Firmware Update Blocked". Nothing is broken, and you have not lost any settings.
To get the firmware on your Puck 2 updated and clear this alert, you need to plug in the Puck 2 or temporarily replace the batteries with a new pair of AAA batteries. Once the firmware update has completed, you can reinsert the older set of batteries. During a Firmware update, there is a much higher demand on the batteries, and batteries that would otherwise control your Puck 2 with no issues will not be sufficient.
Is my Puck still working?
More than likely your Puck is still working. A Puck that is blocked from a firmware update keeps running on its current firmware: it still reports temperature, still controls your rooms, and still talks to your vents. The only thing that your battery levels likely affected was the firmware update. The firmware will not update until the batteries are replaced or the Puck is plugged in.
How do I resolve the "Firmware Update Blocked - Critical Battery" alert?
- Open the Flair app and look at the Pucks in your home. A Puck with a low or critical battery is flagged there, which tells you which device to go to.
- Put fresh batteries in that Puck. Follow the steps in replacing your Puck's batteries for the correct battery type and orientation.
- Leave the Puck alone for a few minutes so it can report its new battery level. Once it reports a healthy level, it becomes eligible for the firmware update again.
If the Puck is somewhere you'd rather not keep changing batteries, you can run it on USB power instead. A Puck powered over USB is not subject to the critical-battery block.
Which device is the email talking about?
The subject line names your home, not the individual device — so "Flair Firmware Update Blocked for [your home]" can refer to any battery-powered Puck in that home. To find it, open the Flair app and check the battery status on each Puck. If more than one Puck is low, replace the batteries in all of them.
I replaced the batteries, and I'm still getting the alert
If the notification comes back after fresh batteries:
- Confirm the new batteries are actually new — batteries that have been in a drawer for a long time, or that came from a multipack where some were already used, can read as low right away.
- Check that the batteries are seated fully and facing the right way. A single reversed or loose battery reads as a dead pack.
- Check the app again after a few minutes to see whether the Puck's reported battery level has actually gone up.
If the battery level in the app still reads low with known-good batteries installed, contact Flair support and tell us which room the Puck is in and what the app is showing. That pattern usually means the Puck itself needs a closer look rather than another set of batteries.
I got "Wi-Fi Issue" or "Download Issue" instead of "Critical Battery"
Those are different versions of the same notification, and batteries are not the cause:
- "Flair Firmware Update Blocked for [your home] - Wi-Fi Issue" means the device could not stay connected well enough to receive the update. Start with your Wi-Fi and device connectivity troubleshooting.
- "Flair Firmware Update Blocked for [your home] - Download Issue" means the update itself did not download successfully. This often clears on its own on a later attempt; if it keeps repeating, contact Flair support.
How is this different from the "Firmware Available" alert?
They are opposites. A Firmware Available alert tells you an update is ready for your system. A Firmware Update Blocked notification tells you an update was ready but could not be installed — in this case because the batteries were too low.