BACnet Input shows "Out of Service". When attempting to set a value or remove the out of service flag an error is seen.
"An attempt has been made to write to a BACnet property with a value that is outside the range of values defined for the property."
An xP Module attached to the Controller was malfunctioning and the inputs on this board were not functioning.
Powering everything down, re-seating the xP Module board and powering the Controller back up resolved the problem.