All my inbox emails disappeared from the inbox. I have a POP3 server connection. The emails are still on the server but Thunderbird will not synchronise them. New emails still arrive. What is going on? I do not want to use IMAP. How can I get Thunderbird to re-download them?
Try creating a second profile in Thunderbird. Do they download cleanly there? If yes, it should be safe to remove the original profile if it's only the Inbox and no local folder with email saved in them.