please help me change my thunderbird password, already changed on ptd

- What is "ptd"? Is your email provider? Simplest method is to go to <Settings | Privacy & Security | Passwords | Saved Passwords> and delete all lines that reference your username on this email provider. Then re-start Thunderbird and you will be prompted for your credentials on startup, so be sure to have them handy. Keep in mind - if you use Normal Password as the authentication method for this account, certain email providers require an "app password", which is separate from your regular login to that provider's web site. The app password is created on their site.