After installing latest PRTG rel. 188.8.131.5270, all Windows Update Status sensors stopped working properly. I get the following error message : XML: The returned XML does not match the expected schema. (code: PE233) -- JSON: The returned JSON does not match the expected structure (Invalid JSON.). (code: PE231) I'm using PowerShell 3.0 on Probe and target systems as previously recommended. Many thanks for your feedback.