If your device is reporting a broken (or "unhealthy") SD card, there are two likely causes:
The SD card is physically not present or has been removed
The SD card has become corrupt and cannot be written to
To diagnose the root cause, you will need to be physically present at the device. If the SD card is not connected, then push the SD card into place. When the next data point arrives to the QuantAQ Cloud (5-7 minutes), you should see the error message disappear. If the SD card is connected properly and the error message persists, the SD card is likely corrupted and should be replaced. To replace it, you can use any FAT32-formatted SD card, though we recommend a 16GB card.