You have one space missing, whichis not that tragic.
But there is a ) missing at the end.
String Info "Info [%s]" {http="<[http://192.168.178.30/data/Dynamic.xml:10:XPATH(/Devices/Device/HEATAREA[@nr='1']/T_ACTUAL/text())]"}
Do you have a look into the logs? Do you use VSCode with openHAB Plugin?