[USPS] Is enrollment in the Manifest Mailing System required for fetching rates/creating labels?

[Greg Melillo (GDM95)]

I've done my Business Customer Gateway onboarding, enrolled in EPS, created my app in the USPS dev portal, and used the provided keys/ids to create a carrier connection in Karrio.

When fetching rates I get:
InvalidApiKey: The client application credentials provided in the request are missing, invalid, inactive or not approved for access.

I'm assuming I need to fill out this form below:
https://postalpro.usps.com/storages/2017-02/MMSAPPLICATION.pdf

Then once approved, I will be able to use their API fully. Is that correct?

[Dan (danh91)]

Hi Greg Melillo (@GDM95),
That’s the case for some carriers, live mode (production ) sometimes requires approval.
I would recommend you try getting a sandbox API key and test with Karrio in test mode to be sure.