USPS Error: "The phone number of the Source address is invalid. Please verify the phone number is correctly formatted and includes the area code."

Based on the error message, the Phone Number on your ship from address seems to be invalid. The ship from address could be your company address or the location set on the order if you are using Multi-Location Inventory.

As a solution, please follow these steps:
 
a. Open the Sales Order and verify the Location.
b. Go to Setup > Company > Locations > click the Edit link of the Location.
c. Verify that the Phone number is valid