Remote GPIO Error

Hi,

I’m new to home assistant and am trying to control some GPIOs on a second pi. I’ve followed this page and have now got it successfully telling me the state of my three GPIOs. However, when I try and use the switch, I get the error ‘Failed to call service switch/turn_off. cannot set state of pin GPIO16’. I get this error for all three of the pins and have checked that I am using the correct GPIO numbers which must be true given the state is updated successfully.

Does anyone know why 'm getting this error - I’m thinking it must be a permissions thing…