Problem

I have tried printing a FedEx shipping label and am seeing following error returned:

Error: Package 1 - Special service SIGNATURE_OPTION is invalid. (PACKAGE_INDEX=1 SPECIAL_SERVICE_TYPE=SIGNATURE_OPTION)

Solution

This error is being returned because FedEx requires a different value for 'SignatureOptionType' Order Extended Property from what was currently submitted.

Please see list for available values and assign a different option: 

Related articles:

Order Properties for FedEx integration