What can I do if M1800 2/3pack can't pair succesful？

Recently, some customers have encountered the problem that MESH cannot be established when using the M1800 V2.0 2/3 package. This problem occurs after upgrading firmware version 1.16.15 or 2.0.8. There are 3 solutions to this problem:

(1) Update all the routers to the lates firmware version which can be downloaded here. （Recommended）

(2) Use the U1 router to be the main mesh router. 

1. Check the firmware version of your router. If the firmware version is the 1.16.15 or 2.0.8, follow step 2.
2. Remove the internet ethernet cable from the current main mesh unit. 
3. Reset all the units to factory default.
4. Check the bottom label of the product，find the unit which marked as "U1"。
5. Configure the "U1" unit work as the main Mesh to access the internet.
6. Waiting for the LED of "U1" unit become solid white.
7. Power on the other units and push the pair button to build a mesh network.

(3). Update the old version of beta firmware 1.16.14.  which can be downloaded here.