Despite continuously generating a new app password icloud does not accept the code.

When trying to authenticate an icloud account with calendar scopes:

UserRecoverableConfigError('Unable to connect to caldav server. Please check the username is correct, and that you are using an app-specific password. https://support.apple.com/en-us/HT204397

Endpoint / Log: 

• Upon authentication

Causes

•  Strange Apple icloud behaviour, where the calendar doesn't update.

Resolution

•  Do not delete the old value in the security screen, instead generate a new app-password with a different identifier (alias) - use this when authenticating.