When you update your Stamps.com account password on the Stamps.com side, you’ll need to update the password on the ShipEngine side as well. Otherwise, you’ll see an error like this below when getting a rate.
Click Edit beside the Stamps.com account that needs an updated password on your Carrier Management page.
In this new window, click Reauthorize.
Here, enter your updated Stamps.com password.
Once you click Confirm, you’ll be able to start shipping with Stamps.com again!