As suggested by you and Chris, I have patiently shorted 9+10 and the light started to blink RED. Subsequently I have turned off the bts and removed the shortcircuit.
However, after turning it on again, the situation is always on ORANGE stable/not blinking light.
Right now I am reading the manual and it says:
"LED_SELF_TEST, Orange Steady, From power on until end of backhaul power on self-test"
I am wondering what else could be the problem. Maybe the MacGyver's way to short-circuit didn't work properly. (I am going to look for a proper RJ-69)
I have also noticed that if I don't plug it into the router, the BTS shows a RED stable/not blinking light.