You must have installed the universal version firmware, there is suitable WDR3600 firmware for Maxis fiber network in TP-LINK Malaysia website, you can try it....

I have installed version 1.1 which is working good. Here's the link: https://play.google.com/store/apps/details?id=com.tplink.tether

virshu wrote The good part, I was pleasantly surprised how easy it was to set up. The sad part is that Guest network stopped working. I can see it in the list of networks, but when I try to connect,...

I don't think it can work that way.

Maybe you can send this suggestion to their support mailbox. They may consider it.

The latest firmware should have solved this problem , please try it. http://www.tp-link.com/en/support/download/?model=Archer+C7&version=V1#tbl_j