Error code E00007 in live mode Wordpress - WooCommerce - Authorize.net AIM Plugin

[zenpayments]

I manage our Wordpress site and am sitting with our processing guru trying to figure out why the Authorize.net AIM plugin for WooCommerce is not working (we keep getting Error code e00007). We've read through pages and pages of similar posts without success...starting a new thread to hopefully get to the bottom of it with some help from the community.

Please note that I am not a coder, I just know enough about Wordpress to handle the straightforward stuff.  My partner isn't a coder either, but he does know the processing "parts" very well.

We have verified the login credentials, reset them, tried again, etc. and are 100% certain they are accurate, yet we continue to get the same error code. Please let me know what else you need to know in order to have some idea on what to troubleshoot:

(Wordpress and all plugins have been updated to the most current versions)

Thanks in advance for any direction you can give!

[NexusSoftware]

Error code E00007 indicates that invalid credentials, the API Login ID or Transaction Key, are being submitted. If you have confirmed that your API login ID and Transaction Key are accurate, you may need to confirm that you are submitting to the correct URL. If you are using a test account, please make sure to post to the sandbox URL. If you’re using a live account, make sure to post to the production URL.