If you are getting failures for Donors, make sure you check under:
  1. onMessage
  2. Approval
  3. Giving
  4. Select Form that is Failing  and Check Show Failed
  5. Click View
  6. Click on on of the failed transactions
  7. There is an error reason that says Bill To Address is required
This is an easy way to find out if you forgot to include something in the creation of the form that is needed to process it.