The error message (Invalid Customer Reference 1) from Scurri is caused by the Order Number being too long. There are two potential causes of the order number being too long for Scurri:
The Order Number (or Order Reference) has too many numbers/ letters.
The Client Short Name is being added to the order number causing too many numbers/ letters.
Client Short Name
The Client Short Name can be added as a prefix to the order number, making it too long. To resolve this, please follow the steps below:
Click Shipping Management then Extras.
Next, click Courier References.
Find the courier being used then click Edit.
Click the Reference1 dropdown and change to OrderNumber.
This should stop the client's short name from prefixing the order number.