This is a known issue when Orion runs in single tenant mode (i.e. without -multiservice enabled). Please use the following configuration at FreeBoard:
Fiware-Service: ' ' (i.e. a whitespace)
(Side-note: XML is deprecated in Orion and, in fact, next Orion release -1.0.0- will not support it. I’d suggest to stop using it, in favour of JSON).