Errors:
External Document No. exists already
Nothing happens in BC, and the document will fail in Link
Customer not found
If the customer is not found, you get an error where you can find the customer manually and load the order. Remember to set up the customer as described under Setup customer - or else you will get the error again.
Item not found
Same as for customers. Remember to align items with your customer to avoid the same error in the future.
Errors, when set up in job queue
If exchange of documents is set up in job queue, as described under Job Queue Setup, there will not be shown errors in BC continously, but correct orders will be loaded, and incorrect will fail.