v154 Payeezy Error 401 Unauthorized

We've installed the Payeezy plugin and are receiving error 401 - Unauthorized when submitting a transaction.1. plugin version: 0.93
2. Zen Cart: 1.54 (through zc_install)
3. PHP 5.4.43, MySQL 5.6.32-78.1
4. Completed all steps at https://github.com/zencart/payeezyjs. The merchant account was linked to the developer account by First Data.
5. No JavaScript errors shown in console
6. Log on failure is turned on but there is no debug file in logs or cache
7. Error occurs in Contemporary Green theme as well as our purchased theme
8. In the module options, Enable Payeezy JS Module is set to True, Sandbox/Live Mode is Live
9. The api at developer.payeezy.com has both Live and Sandbox selected
A search of the Payeezy forum indicates this can happen if the merchant password entered when linking the merchant and developer accounts, but since First Data did this for us I assume they got it right. Since we only have one merchant account and one API, I'm sure we have the correct authorization information entered.

Lem3:

....but since First Data did this for us I assume they got it right. Since we only have one merchant account and one API, I'm sure we have the correct authorization information entered.

i think this is a bad assumption. i would re-look at the credentials because i'm pretty sure something is wrong....

good luck!

If you're getting a 401 Unauthorized response, then First Data should be able to see the incoming transaction attempt on their end, and should be able to give you specific details about the failure.