The unit is usually in the process of starting up or resetting when a TPLink flashing white. 

• This action is intended to inform the user of the system's state and is a component of its standard operating indications. 
• The flashing deco white light usually indicates that the device is changing between states including turning on rebooting or reconnecting to the network rather than a problem.
•  An unfinished setup procedure or trouble establishing a steady connection to the network or modem might be the cause of the Deco device blinking white for a long time.
• This could happen if there is a power outage or if the internet supplier isn't giving a steady signal. 
• Users may fix this by making sure the modem is operating properly and that all of the cords are firmly attached. 
• Additionally persistent flashing may be fixed by doing a factory reset or restarting the Deco device.
•  Find the reset button usually on the back or bottom of the device and push it for ten seconds or so until the light changes to reset the device.
•  Once the system has been reset, reconfigure it by following the steps provided by the TP-Link Deco app. 
• Make that the primary Deco unit is positioned for best signal spread and is connected to the modem.

Visit our website to know more about it.