Question: I am trying to sync my iCloud calendar with Dubsado, but it is saying that Apple doesn't recognize it. However, I believe I'm entering the correct login credentials. Any advice?
App-specific passwords allow you to sign in to your account securely when you use apps that don’t natively support two-step verification or two-factor authentication.
When your Apple ID is protected with two-step verification, or two-factor authentication, you'll need to use an app-specific password to sign in to your account using any apps or services that don't support entering verification codes. This maintains a high level of security and ensures that your primary Apple ID password won’t be collected or stored by any third-party apps you might use.
Generate an app-specific password
Sign in to your Apple ID account page.
In the Security section, click Generate Password below App-Specific Passwords.
Follow the steps on your screen.
After you generate your app-specific password, enter or paste it into the password field of the app as you would normally.
Taken from Apple.com