My Olympus voice recorder WS is suddenly not recognised as an external disc when connect to my imac

My olympus voice recorder WS 853 still records & plays back perfectly when used to record voice or phone calls. But it suddenly is not recognised by my imac running on OS 10 13.6 High Sierra. Disc utilities shows no sign it is there.

I've contacted Olympus & they have no explanation. Has anyone experienced a similar problem ? I suspect it is one of those dreadful OS updates that means the Mac Os refuses to recognise the external device. I had that precise problem with a ten year old Canon printer. Canon refused to continue writing software updates & apple kept on requiring it by interfering with the Canon software. It is truly appalling the way the computer industry behaves.