check_window - 'NoneType' object has no attribute 'format'

[mzbedat]

Hi,
I have this simple code:

Open Browser ${LOGIN_URL} gc
Open Eyes Session ${LOGIN_URL} ${Applitools-AppName} ${Applitools-TestName}-${Platform}-Login-Success ${Applitools-Key} ${Width} ${Height}
sleep 5 sec
Check Eyes Window Testing

But when reaching the Check Eyes Window its failing inside the check_window (eyes.py) with this error:
'NoneType' object has no attribute 'format'

What am I missing?