They released a beta firmware a while back. You can download it here. Be sure to read through that thread (currently 12 pages) to see what issues people have been experiencing with it.

 

https://community.tp-link.com/en/home/forum/topic/261318

This is very very sad. I bought a top of the line router from a well known manufacturer hoping to develop a mesh network at my home. I can see that this thread is now well over one year old, and you could not figure this out. I am trying to use a TP Link mesh extender with the top of the line TP Link router and they can't connect as intended. And you keep this situation unresolved for over a year. You should get your "sht" together, or just get out of the game. Hello ASUS! New customer on the horizon.

@Bantapudu 

Same situation here. I've read everything through and through, and for the life of me, I can't set up a mesh network using my AX11000 or my re650's.

Hopefully, once a non-beta is released, this will be resolved, but I am highly dubious that will ever come to fruition.

 

These will be my first and last TP-Link products ever and will either go back to ASUS or Netgear. I am just so sick and tired of dealing with the BS by this manufacturer.