All my group members have disappeared. Is there a way to retrieve them?

Unfortunately Christine, this has been going on since Dec at least.  Microsoft are, apparently, working on it, tho they do not deign to tell anyone.  If you look for Deb Rodgers posts, you can find the way to contact a real person in Msoft, and they will undertake remedial action.  But it wont work, at least it didnt for Deb or myself.

My advice is to create your groups on Word and cut and paste them into Outlook when you need them.  At least then YOU have control over their security.  And not to trust Msoft, until you are sure that they have sorted the problem - probably never...

Fortunately I had saved the folders to another location on y computer as I do not trust Outlook anymore and I recommend that everyone else  do the same.

I clicked on FILE, then SAVE AS and saved each new one as I made it to a Documents folder. It is easy to click and drag  a copy back into the Outlook Contacts folder and still retain the saved folder in the new location.

This is appalling and I  did not expect to lose all my Contact Groups twice.

You seem to be referencing Office Outlook. This thread is about Outlook.com. Not the same thing.

My contact groups disappeared from  both Outlook.com and my  Microsoft Office Outlook but point takendid back them up through O, I  did reinstate them in Office.

Contact groups in Outlook.com map to categories in Office Outlook.