User Profile Service Application - Operation is not valid due to the current state of the object

When you  see the following error message, user profile incremental synchronization failed operation not valid due to the current state of the object. The reason why this error showing due to User Profile Synchronization Service is not running on server. We need to start the user profile synchronization service.

To fix this:

1. Browse to Central Administration

2. Go to System Settings --> Manage Services on Server

3. Select the server from the top right corner where the User Profile Synchronization Service is running.

4. Find the job in the list and it should be in a "Stopped" state 

5. Click on Start

This can take up to 15 minutes to get started so be patient. Once complete, try running a sync again.