XML.Set Element Text not working

Get Element Text ${Parsed_CapaUpdate_Hes} .//capability[code=‘${CapabilityCode}’]/value works, rendering the current value “Off”
Set Element Text ${Parsed_CapaUpdate_Hes} .//capability[code=‘${CapabilityCode}’]/value ${CapabilityValue}
does NOT change the value to “2”, executed in same keyword immediately after the Get Element Text
${Parsed_CapaUpdate_Hes} was parsed by
“${Parsed_CapaUpdate_Hes}= Parse Xml ${CapaUpdate_Hes}”
xml string has default namespace declaration xmlns=“http:…”
${Parsed_CapaUpdate_Hes} is a global variable in RFW resources.

do you have any clue why?