The error (Unable to Add Comment to Order) can be caused by one of the following reasons:
Changing the Courier Service within the order details instead of the Scan Actions page.
Changing the order number within the order details but it already exists in Mintsoft.
For 3PL Databases the same order number can be used for different clients but not the same 3PL Client.
Changing the Courier Service
To resolve this error message, you would need to change the courier service in the scan pages screen and not in the order details the below steps will go through how to do this without getting an error message to appear:
Click Order then Overview.
Find the Order, click Actions then Pick Order.
On the Scan Actions page go to Change Courier Service section.
Select the Courier Service you want to change to.
Click Update.