I get a processing error when I attempt a transaction

Processing error messages are usually received while a merchant is in the process of integrating.

The most common causes are that an unknown character is being included in the values for the parameters, or no value is being supplied at all. For example, consider the following HTML:

<input type="hidden" name="instId" value="#12345">

The # symbol would cause an error to occur when the content of the form is posted to our payment page, because the server is not expecting the value of instId to contain a non-numeric character.