Can't get past 10002ErrorSecurity errorSecurity header is not valid

I checked for spaces, I recreated the API credentials, I turned off Sandbox everywhere it's supposed to be turned off, by double clicking on the on the behavior and also by scrolling down the code on the checkout pages, confirm pages, failure and success pages etc. But I still get the error? This website is supposed to be up today, in fact this right now, but I can't get past this issue.

This error means that there is a problem with the api credentials.

It will happen if you are using live api credential in the sand box, or using sandbox api credentials on the live server.

It will also occur if you have not yet accepted the paypal billing agreement

Sometimes, paypal just generates bad api credentials. try generating new api credentials for your account and using those.

I regenerated the API but no go! I called Paypal tech support and they deny that the API credentials could be bad. They keep insisting that the shopping cart is trying to use the sandbox with live credentials or live credentials with the sandbox. I checked everything tens of times and it should all be on the live credentials. I'm screwed. This site went live today and people are trying to order but can't. Can you open a support ticket and call me asap and see if you can pinpoint the problem for me?

I have created a support ticket so we can look into this issue further.

To view and edit your support ticket, please log into your support history:
supporthistory.php

If anyone else is experiencing this same issue, please append to this thread.

Thanks for opening a support ticket for me. After much going back and forth with Paypal it turned out that the problem was with the ampersand on the email address. We finally got around it and it's working as of an hour ago. We already got two orders, but....

The issue I have now is that the credit cards (at least in the two first and only orders that just came in), are getting charged twice. I'm not sure if there is a problem with the code, or if the buyer is pressing the checkout button 2x consecutively. If so, is there a way, through the code, to get it to ignore more than one click?

I'd appreciate your help with this or we'll have to keep reissuing refunds.

Thanks.

respond to the support ticket i started with the requested information so i can take a look.