Beginning June 15th, Apple will begin requiring App-Specific Passwords for connecting calendar syncing. If you're having some trouble connecting your iCloud calendar to Acuity, be sure you're using your iCloud user name and an App-Specific Password when connecting. Give the below steps a shot -- a lot of times, this will solve any connection issues!
Create an App-Specific Password for Acuity:
- Pull up your Apple ID account page
- Under the Security section, if you see App-Specific Passwords, click "Generate Password" and follow the steps. Otherwise under Two-Factor Authentication, click "Get Started..." and follow the steps, then come back and follow the steps for creating an App-Specific Password.
- Use the new App-Specific Password you generated in the previous step when connecting Acuity and iCloud.
You can read more on that in Apple's help article Using App-specific Passwords.
Also, keep in mind that iCloud events 200 days into the future will sync once this is set up.