What version of OH do you have? In 2.3 there is a problem with MCP23017 binding but here you have workaround Problem with new MCP23017 binding in Openhab 2.3 - #11 by aogorek
I use this binding MCP23017 - Bindings | openHAB
What version of OH do you have? In 2.3 there is a problem with MCP23017 binding but here you have workaround Problem with new MCP23017 binding in Openhab 2.3 - #11 by aogorek
I use this binding MCP23017 - Bindings | openHAB