When submitting an order online via Test or Sandbox web store account, user might encounter a system maintenance error.
To resolve this:
1. Login to the Test or Sandbox account
2. Navigate to Setup> Site Builder> Setup Website> Shopping tab
3. Set the Require Authorization for Credit Card Transactions = F
If the error still persist, check the value of Send Email To (Separate Addresses with Commas)
4. Navigate to Setup > Company > Email Preferences > Sandox and Release Preview section
5. Make sure that email addresses are separated by a comma (,) and not a semi-colon (;) on the Send Email To fields.