Hello ajeppe.
Thank you for using Apple Support Communities. It sounds like you need help generating an app specific password for your Apple ID. If so, we'd like to share a great resource that includes helps steps you can try. Click here: Sign in to apps with your Apple ID using app-specific passwords - Apple Support
How to generate an app-specific password:
1.) Sign in to appleid.apple.com
2.) In the Sign-In and Security section, select App-Specific Passwords.
3.) Select Generate an app-specific password or select the Add button
, then follow the steps on your screen.
4.) Enter or paste the app-specific password into the password field of the app.
If you're unable to successfully generate an app-specific password when visiting the Apple ID website, we recommend that you reach out to Apple Support for help. Just in case, you can use the link below to reach them:
Get Support - Apple
Thank you for using Apple Support Communities. Best of luck.