The MESH block keeps unpairing from my device.

MESH blocks can unpair from your MESH app when the MESH block is too far way from the MESH app. 

MESH blocks use Bluetooth to pair with the MESH app, so the MESH blocks and MESH apps need to always be within 30 feet of each other. Also keep in mind that physical obstacles (e.g., walls) and nearby wireless devices can also interfere with the Bluetooth connection. Try repositioning the MESH block and MESH app within 30 feet of one another with a clear, unobstructed path.