Im posting this for those who may have stumbled into this problem and can’t find the way out.
Out of curiosity I connected the Clip + to an android tablet as OTG usb to see if any app there would play the playlists.
None of them did,… so experiment failed,… can’t expect everything to be possible… can we,…? No problem.
Well,… alas, there was. After disconnecting correctly,… I found that all music and playlists on the clip’s internal memory had
disappeared. Further examination showed them to be present on the device but the clip wasn’t planning to show them to me.
Id put a lot of time into the playlists but had no backup,… so the idea of formatting and re-building was a last option.
Everything had been done on MSC,… and there were no invisible files to be found in MTP mode.
I looked in the root folder of the clip’s internal memory just to see if Android or some music app on the tablet had placed anything there that could be causing the problem.
…and there was an unfamiliar empty folder called μUDIOB~1 ;created at close enough to the same time as I’d tried the thing out with Android.
So I deleted it (and put a copy on the desktop,…just in case) .
Disconnected,… and read “War and Peace” while waiting for the Sansa never to be remedied wonder aka ‘‘Refreshing your media’’,…
and everything was where it should be! Quite a relief.
I hope this may help someone out at some time.
Thanks for the info.-- poorly conducting software deserves a special place in jail . . . .
Good thing though it was after all a happy ending. It helps a lot by the way if you have a back up of your playlist or song files oto just in case. 
