After upgrading to HVR v5.5.0, clicking Menu > Help > User Manual returns the error below:
Error 404: Page not found. The requested URL 'qthlep://hvr/hvr/html/hvrfrontpage.html' was not found in HVR Online Help.
To fix the online help page: Deleted the file named <hvr_config>/files/onlinehelp.qhc.
Removing this file from your environment resolves the problem.