[Reference] The scheduled task is disabled after install

You have just installed Microsoft Azure Active Directory Sync Services (AADSync). You discover that the Scheduled Task in Task Scheduler is disabled.

The Status of the Scheduled Task is determined by what you do with the Synchronize Now checkbox on the last page of the Configuration Wizard. 

Scheduled Task Enabled

Scheduled Task Disabled

If your scheduled task is disabled, simply enable the task to begin your runs every 3 hours.