I've been working on this trail for a bit - and while I undertsand the concepts, I'm stumped on why I'm getting this error: 
 

Challenge Not yet complete... here's what's wrong: 
A Create a Record action for the Closed Won criteria node isn't properly configured. Make sure that it creates a draft contract according to the instructions in the ‘Create contract for closed opportunity’ task action. Make sure that Start Date is set by using a formula.

I've gone over all of the workflow tasks information to recreate the contact. If I activate the process and close an opportunity, it creates a contract with the expected information and the date is 1mo away with 12mo term. The workflow's task (which is the template for the actual contract) specifies the following: 
 

Use the closed opportunity to create a contract for the associated account. 

Account: The account associated with this opportunity
Status: Draft
Contract Start Date: 1 month from today
Contract Term: 12

Here are my actions: 


The Contract Start Date is set to the following formula:

DATE(
    YEAR(Today()) +
    FLOOR((1 + MONTH(Today())) / 12) -
    IF (MOD(MONTH(Today()) + 1, 12) = 0,
        1,
        0),

    MOD((1 + MONTH(Today()) - 1), 12) + 1,

    DAY(Today())
)

Again, for all practical purposes I'm passing this, as it functions and the contract is created. But I must be missing some small detail, named field, something that's tripping up the validation settings. Any help is appreciated!

 

I am beginner :  Not able to solve Trailhead challange for-Developer Beginner :Process Automation-Automate Basic Business Processes with Process Builder
"
Create a process to update child record when the parent is updated.
You've been given a requirement to keep Contact addresses in sync with the Account they belong to. Use Process Builder to create a new process that updates all child Contact addresses when the address of the Account record is updated. This process:
Can have any name.
Must be activated.
Must update Contact mailing address fields (Street, City, State, Post Code, Country) when the parent Account shipping address field values are updated.
NOTE: You may have to deactivate the validation rule for the Contacts object (created from a previous challenge) in order to complete this challenge."

 What I had tried 
Deleted validation rule on contact  from previous challange.
 Using Process builder created new Process with below details
Object: Account
Criteria:'Update Address' with condidtion

Field: selected shipping street, city, state,postalcode and country
Operator: Ischanged
Type: boolean
value: true

Condition:
Any condition met (OR)

 For Immediate action
Action name: Mailing address change
Records: Account.contacts
Criteria for Updating Records:No criteria—just update the records!

Set new field values for the records you update:

Field: selected Mailing street, city, state,postalcode and country
Type: Reference
value:  selected shipping street, city, state,postalcode and country

 after this saved and activated. So Once I check challange got below error:
"Challenge Not yet complete... here's what's wrong:
An update to an account record failed to update the mailing address fields of all child contact records. Make sure that the process is correct and that it is activated."

So Please help.