@CCDan  I wasn't able to wait and did the as in the instructions. Problem is that X50 outdoors are now stuck with green led blinking since more than 30 min.... what next? WOuld I ever being able to recover them? How?

  @CCDan I succeeded for some. Reason is with last firmware it returned to old habit of showing online the devices (or not) and not allowing them to connect to internet or not showing them but they are communicating ok in internet or even worse, oscillating between connecting/disconnecting devices. Fully unstable network.

Now, from 4 M5 and 2 X50 Outdoor are working 3 M5 and 1 X50. 1 M5 it looks to be dead but not had enough time to recheck...

Anyway, bad decision to upgrade, in my case. You know your luck what is: in Romania mesh network is quite new for residential and consumer producers like Asus or similar, they don't have support. I am now talking to Cisco to check their mesh system but NEVER buy again mesh under company name - this is a suggestion for EU buyers  as you cannot return them if you buy them on company name... Anyway, I decided to replace TPlink, just that I need to work in between and find the best solution that may work normally.