Gmail – how do I get entire Inbox in Thunderbird?

My Gmail account is configured in Thunderbird, all works fine except – the oldest email I can access in Thunderbird from Apr 2021, while my account is almost 20 years old.

Settings:

  • imap.gmail.com on port 993 using SSL/TLS and OAuth2.
  • Copies & Folders > Message Archives > “Keep message archives in” is checked, Using “other”: “All Mail on mymail@gmail.com”.
  • Synchronisation & Storage > “Keep messages in all folders for this account on this computer” is checked.
  • Disk Space “Synchronise all messages locally regardless of age” is checked. Changing it months or years makes no differences, no additional mails are downloaded
  • The local directory at /Users/Me/Library/Thunderbird/2ravxxx.default/ImapMail/imap.gmail.com is around 800MB in size, while the “online” inbox is around 15GB.

How can I get all my emails in to Thunderbird?