When processing orders you might come across the "Hard 121500 - The selected service is not valid with the selected packaging" error.
This error is shown when the service chosen to ship is not compatible with the selected packaging type, you will either need to change the service level, or change the packaging.
If you wish to change the Service Level, follow the instructions the article: How to change an order's Service Level.
If you wish to change the packaging, you can either:
a) Delete the batch, change the packaging type for the order in the WMS and reimport
b) Delete the batch, change the Packaging type for the Billing Account on the Client level and reimport (not recommended unless the change applies to all the orders, since this will affect every other order imported under that client and related to the billing account)