Where are you seeing dozens of incoming messages being downloaded, in the Status Bar in the lower left corner of the main window? Do you have several email accounts and which tab is active when you start Thunderbird?

I have several email addresses. NONE of them are receiving. I have tried uninstalling TB >> restarting >> re-installing. I've deleted ALL of my accounts from TB >> uninstalled >> shut down >> restarted >> reinstalled >> imported just 1 account. When I imported the 1 account, it went thru the routine of "downloading X of X messages" but it didn't actually download anything It says I have unread messages in the inbox and the spam folder, but the inbox has no new messages and the spam folder is empty.

Your quick filter is set 1) to show only senders in your address book, and 2) to apply this setting to every folder. De-select the two things that are selected in the quick filter (the buttons with the blue bars).