On attempt to place Sales Order for a new Office 365 subscription the following error appears:
"One or more required fields are empty or filled incorrectly, please try again."
Incorrect Service Parameter configuration of corresponding Service Template.
Correct Service Parameter configuration as per Creating 'Office 365' Service Template documentation article, step 12.
Also, recheck that all the Configuring Office 365 Subdomain Form for OA Billing documentation article steps are done.