IDoc could not be sent

What causes this issue?

Several IDocs were to be sent to the Internet address in one block. A
conversion error occurred in at least one of the IDocs to be sent. As a
result, the whole block was not sent.
This IDoc does not have a conversion error.

System Response

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

How to fix this error?

You should process/send the IDoc again.

Error message extract from SAP system. Copyright SAP SE.