How to add additional unleashed device ?

[tw_uems]

I have 2 R310 devices in office.
Both was working fine.

I upgrade both to 200.7.10.2.339.
Master was upgrade successfully but another one was fail.

I see slave device was disconnected in dashboard. OMG!

I upgraded slave R310 to 200.7.10.2.339 manually but still disconnected.
I removed it from dashboard then reset but still can't map the mesh network automatically.

It always in normal unleashed setting page.
How could I do?

Re-create mesh network?

I will add other one R310 into mesh network in few month.
I need re-create again at that time?

[hyosang_choi]

When AP do upgrading, Mater send URL to the AP to upgrade.

Thus the AP have to configure DNS IP.

First please confirm about it on another AP.

[tw_uems]

I already done DNS setting when I done the unleashed setting 1 year ago.
I remote in dashboard by master device IP then use dashboard upgrade bottom to do upgrade.
After upgrade done, dashboard say slave device upgrade fail and disconnect.

[tw_uems]

I reset all of three device to make them in a unleashed group.