so you are saying you have a problem with your Apple operating system. I would expect Apple to be the ones that would answer questions about OSX.

My guess is some new security thing like they did a couple of years ago and you have to find some switch to allow Thunderbird access to the mac address book again.

And you were OK when using 10.13.1??

Thank you Matt. I did find the location and switch to allow Thunderbird to access the address book but the Mac address book was not an option. It would not allow me to input it either.

Thank you Wayne. Yes, Thunderbird worked fine before the upgrade.

Please file a bug report at https://bugzilla.mozilla.org/enter_bug.cgi?product=Thunderbird

Bug report completed. I hope I did it right. Several other issues are occurring as well. Unable to move and email when composing and ALL the dialog boxes are taking a long time to open and load, some never load, or no information loads at all. I've reported it all. Thank you for you time Wayne.

mslinnea said

Bug report completed. I hope I did it right.

Yes you did. thanks. https://bugzilla.mozilla.org/show_bug.cgi?id=1428651

Update your Thunderbird! for people having the same issue.

I wish there was an UPDATE option available so one could check it every so often.

Thanks for the update.

Update checking is as Help > About (ditto for Firefox)

Nope, no such animal on Thunderbird or Firefox. Help>About. Does not exist. My options are; Help> Thunderbird Help Troubleshooting What's New Release Notes

I'm told for Mac, it is

 menu "Thunderbird" > "About Thunderbird"

Excellent, thank you Wayne. Have a Happy New Year.