Ooops, took us a while to realise, but there was a bug in the shvps v9 firmware that can lock the unit in either DC or Off, with no possibility of generating switching or custom waveforms. This has been fixed in version 9.1 which is now included on the download page. It can be accessed directly from here: https://osf.io/cxmqb/
If your HVPS is using firmware 9, you should upgrade to 9.1
Bug correction in the shvps firmware