The Folder Pane is hidden. Enable it under View/Layout.

Thanks. But I still don't see my emails. I click on View->Layout->Folder Pane I get the screenshot below. It looks almost identical to the screenshot I sent in my first post, except there is a blank column on the left. Where are the emails? Where is my inbox? Where is my sent folder?

When I click on that big box labeled email, nothing happens.

I've no idea why a new setup fails to show the standard folders, unless there's some 3rd-party security/VPN/antivirus affecting it.

I don't know if this has any connection or sheds any light on the problem, but when I send a test email using TB to another email address that's not in TB, the email is sent by TB and received at the other address. But TB gets hung up trying to save a copy to the "sent" folder. When I finally click the cancel button, I get this message:

"Your message was sent but a copy was not placed in your sent folder (Sent) due to network or file access errors. You can retry or save the message locally to Local Folders/Sent-youremail@youremail.com."

Then there are 3 buttons, Retry, Save, and Don't Save.

Who is the mail provider? Some of them, such as gmail and outlook.com, automatically copy sent messages to a folder, so you must uncheck 'Place a copy in' in the Copies & Folders section of Account Settings, to avoid this error.

To see if the display issues are absent in safe mode, hold Shift when launching TB.

What is the antivirus and its mail settings? The TB profile folder should always be excluded from AV scanning.

I don't know why, but after I closed TB & opened it again, my folders appeared.

Also, I tried sending another test email. This time, a copy was saved in the sent folder.

So, everything seems to suddenly be working.