Which version did you upgrade from? For some time, Thunderbird has had a virtual address book, All Address Books, which is a composite of the separate address books. This virtual address book allows you to search all your address books as if they were one big list. But the original address books should still be there, presented as if they were subfolders.

I cannot find the original subfolders. I suspect they are .ldif files just don't know where. Pointers please. I have auto-upgrade so always on the latest available version. 52.0 loaded 4/4/18

McAfee has been very problematical with Thunderbird for about 5 years. It is to the point now that I just shake my head and say just get rid of it.

But this address book thing. What is the address book everything is in called? "All Address Books" perhaps? Try double clicking it.

There is no name on the address book--just "Address Book" There is a notation that says "Total contacts in ALL ADDRESS Book" Double click to open or on the bottom of the list simply reloads the ALL list. Frustrating. I looked in my Profile, but no help there. Worst case I create new Collected, Personal and Mail books-----tiresome.

Just checked Add to mail List. The choice of where to add lists my Collected, Personal and Mail locations, but I can't see how to get to them . Obviously they are there, just hard to find!!!!

Restart Thunderbird using the option on the help menu to restart with add-ons disabled. I have a feeling you might have an add-on that did not transition versions very well.

The restart with add-ons disabled let the three address book show and become active. I will shut down and restart in normal mode, just to be sure.

It appears I have an unwanted add on--issue does not go away so I will edit add-ons and report back if that does not completely remove the issue. Thanks to all for excellent responses.

I have disabled McAfee Anti Spam and now all appears to be good. I had Support advice to dump McAfee which I will now do. Also Mat's advice on add-ons was exactly correct so sincere thanks to the talented pool of helpers. I did take a night off to "sleep on it" that always seems to work for me.