Marketpress error: problem connecting to PayPal to setup your purchase

hi there

I'm running a couple of multisites with marketpress installed.

One is setup only for chained payments and the other not chained.

I'm getting an error on both sites when trying to double check the payment process.

There was a problem connecting to PayPal to setup your purchase. Please try again.
520003 - Authentication failed. API credentials are incorrect.

For this exercise I'll work on the not-chained site.

It's nearly 4 years old now and has a number of plugins installed.

I've deactivated all plugins except marketpress, pro-sites & mycustom css.
Have also switched to twenty-twelve theme.

I've also switched it to chained payments, and then I get this error: There was a problem connecting to PayPal to setup your purchase. Please try again.
10002 - Authentication/Authorization Failed - You do not have permissions to make this API call

Am wondering if this has anything to do with not having an SSL Certificate

Nothing seems to be helping