Stumped and would appreciate suggestions. I have listed below each step that I have done on my end so that Michael or others can follow 
I have multiple email accounts that I want to archive via EF and remove from the associated servers.
I have created a new library for testing purposes. The EF window for that library folder is open.
I started with the easiest email account for testing purposes - it should be very rapid I am assuming (it’s new and only has 8 emails in the inbox and 2 Sent messages). There are no draft messages, no junk mail and the delete folder is empty.
I have Mail opened (using Sonoma 14.3.1 (23D60)), Spam Sieve is running also, and within the Mail app I scroll past Favorites on the left side of the screen (in Mail still) until I reach the email account I want to test, listed under On My Mac.
I click with my mouse on the email account, but it stays grey (it doesn’t seem like I can select it). For what it’s worth, I can select the mailbox if I try in the Favorites section of the Mail menu on the left side of the Mail app - I still get the same results though - I press F1 after selecting the account - nothing happens. So, trying to import by mailbox doesn’t seem to work?
I can select all 8 messages that appear in the inbox with Ctrl-A and then try F1 - nothing happens.
If I click on a single message in the Inbox and click the F1 key, nothing happens also. If I click on option-F1, strangely, the system settings window for Displays appears. I guess that this key combination is being used by the system?
If I drag any message of the 8 available into the EF window, the message successfully appears/is copied in the Record list.
To continue testing, I delete the test message (and I empty the trash).
If I select all 8 messages (ctrl-A) and drag them into the EF window, I see an icon on the mouse cursor with 8 messages appearing in EF but after dragging over all 8 only 1 message appears (and it’s always the same one, dated February 27). EF gives me a message that it has successfully imported, but it’s only one email that appears. The other 7 messages don’t appear.
I can individually drag each message from Mail to the EF window though - I dragged all 8 into EF and they all appeared and seem complete.
Just in case, I tested using the Favorites portion of the Mail menu to select and get exactly the same results.
I am using a Logitech MX Keys S keyboard with my Mac Pro 7,1. I thought that it might be the keyboard not working correctly with the F1 key but after reconnecting the Magic Keyboard that came with the Mac Pro, I get the same results, including that Option-F1key combo calling up the display menu in Settings.
Right now, I can’t proceed forward. One of the email accounts that I want to archive has 33K messages in it so I don’t see myself dragging in each of those messages into the EF window, haha.
Any ideas or advice, things to try etc. much appreciated! I hope the explanation of what is happening is helpful and appreciate your patience if you have read this.
Thank you.