I post here my question just in case is helpful for somebody else. My problem was that my colleague was connected to the same device and I was not able to connect to the same device.
Note: I had this problem with Amazon Fire TV connecting over Wifi.
There are 2 solutions:
Easy to "drop" his connection (sorry buddy :)
Restart the device
adb kill-server
adb start-server
adb connect device-ip
A bit more difficult but two clients can use the same device (use different TCP ports)
Please look at this answer