As noted elsewhere, PayPal makes it nearly impossible to find your already acquired API information for your shopping cart to work. It is NOT intuitive!
Log on to your PayPal merchant or business account;
Click on Activity in menu at top (really, this should be under Account Settings);
Under Operations, select API Access;
Scroll down to NVP/SOAP API integration (Classic);
Select Manage PayPal checkout settings;
You will be taken to View or Remove API Signature;
Click on the assorted Show links for:
API Username
API Password
Signature
Go to your Cart in Backlight;
Click on Settings > List Settings;
Click on Edit Settings;
Scroll down to PayPal Live API items under Checking Out section;
Copy and paste your API credentials and be sure to SAVE when you are done.
I hope this helps others who have been just as frustrated as I trying to ferret out this information on the new-and-less-user-friendly PayPal website.
Ben and/or Matt may let us know if there are other types of API Access types that Backlight uses. Meanwhile, this should be helpful to many/most of you.
I followed your instructions as closely as possible. Certain options were not exactly as described. The 3 PayPal TESTING options were available in cart settings. I located the API keys on my PayPal account. I copied and pasted then into the testing fields in Edit Cart Settings. I tried to make a test purchase. The PayPal logo appears in my cart checkout but when I click it, I get an error message:
Security Header is not valid Error code 10002
I am not able to paste the API creds into the “Live” API Fields as they are grayed out.
6 hours later and it appears to be working. The paypal logo link works. I guess it just took time. I was not able to do a test purchase. Maybe my wife will buy something to see if everything is go!
I have found that the Sandbox can be flakey and not work now and then.
You should be able to set up a buyer account as well in the Sandbox portal. Once logged in to the Sandbox portal, visit this link and create a card number: https://developer.paypal.com/developer/creditCardGenerator/
You can then use the Sandbox buyer account to checkout through PayPal, and add the card using the generated details from that link.
I have my cat working and integrated with PayPal. All seems to be working now. Others have reported issues with PayPal lately; slow transfers, late reports, etc. Some have switched to Stripe (not on Backlight as far as I know). Does anyone know if Backlight integrates with Stripe or any other electronic funds transfer platform besides PayPal?