I have an error with reference KFVQKOVW. I have already Data.com Assessment App, but i can't validate trailhead. I need to be update in order to show my boss i am doing trailheads. Please, help me how to proceed!

I have completed the Lightning Process builder step and i have verified that it is working correctly ( the battle Station record has been changed to complete and it has post a message to chatter, but when I click the Verify Step button I get this error message:

"Step Not yet complete... here's what's wrong:
An update to a Battle Station record with Weapon Status of 'Fully Operational' failed to post a Chatter message to the record. Make sure that the process is configured correctly and that it is activated.
Note: you may run into errors if you've skipped previous steps."

The validation rule should be on the Case object.
The validation rule should be named 'Mark_as_Escalated'.
The validation rule should fire if someone tries to set a case as escalated and it is closed, closed when created, or does not have a priority of High.
The validation rule should display the error message 'You can only set a case as escalated if it is high priority and not closed' under the Escalated field when triggered.
Add the 'Escalated' field to the Case page layout.