Just installed MarketPress and can not complet a transaction

Can not get MP to complete a transaction - error code 10002 see screenshot below using paypal ex

when using authorized.net in firefox we get - "The page isn't redirecting properly
Firefox has detected that the server is redirecting the request for this address in a way that will never complete. This problem can sometimes be caused by disabling or refusing to accept

or (in chrome)

"This webpage has a redirect loop
The webpage at https://photojurni.com/store/shopping-cart/shipping/ has resulted in too many redirects. Clearing your cookies for this site or allowing third-party cookies may fix the problem. If not, it is possibly a server configuration issue and not a problem with your computer.
Here are some suggestions:
Reload this webpage later.
Learn more about this problem.
Error 310 (net::ERR_TOO_MANY_REDIRECTS): There were too many redirects."

I get these responses with download or shipped.

Sure could use some help here!