The error message 'The addGift field is required. Invalid request body.' is coming directly from Raiser's Edge and often appears when trying to add gifts directly to a record. Unfortunately, the error message is fairly generic and doesn't tell us the nature of the issue. Only that there was an error trying to add the gift.
However, if you attempt to add a gift via a Gift Batch, Raiser's Edge returns a lot more information about what was it that prevented the gift from being imported.
Once you have altered your template to add gifts to a gift batch and the error message still in not clear, please contact support@zeidman.info