The error (When Creating TPN Shipment! API Error: Error: the user's customer account is [blank] but the customer account provided is [value]) occurs when the Account Code in your account configuration doesn't match the Account Code in The Pallet Network portal. To resolve this issue, follow these steps:
Click Connect then Courier Integrations.
Click The Pallet Network then click Edit against the required connection.
Ensure the Account Code value matches the one listed within your TPN account.
Ensure both Account Codes match exactly:
Check for any leading or trailing spaces
Verify the codes are identical in both systems
By following these steps, you should be able to resolve the error.