Error using Composer: Could not find a matching version of package paradoxlabs/*

When installing a ParadoxLabs extension by Composer, if you get an error message like:

[InvalidArgumentException]
Could not find a matching version of package paradoxlabs/authnetcim. Check the package spelling, your version constraint and that the package is available in a stability which matches your minimum-stability (stable).

This almost always means the composer keys you are using to authenticate for the Magento Marketplace repository are for a different account than the extension was purchased from. Please look at the account used to purchase, and compare the composer keys from that to what is being used. There can only be one Marketplace account tied to a Magento installation.

Please see Magento documentation on how to find your Marketplace composer keys: https://devdocs.magento.com/guides/v2.4/install-gde/prereq/connect-auth.html

Your saved composer keys will be stored in a file called auth.json, usually located at {magento}/auth.json or ~/.composer/auth.json.

Composer installation will only be available if you purchased from Magento Marketplace. If you bought from store.paradoxlabs.com, you must follow the Store installation directions in the user manual (uploading the files to app/code).