Authorize.net issues …

The error message you provided is thrown by Authorize.net so there should be some trouble in account setup.

Make sure you’ve selected Live Mode from wp-donate settings and used correct API credentials.

For more help about this message you can take a look here and follow the steps https://support.authorize.net/authkb/index?page=content&id=A415&pmv=print&impressions=false

If this will not help then please provide some more details so we can find why this error shown.