I have installed the new version of Store (2. whatever) and created a test "store" complete with products.  I want to test the PayPal process.  I checked the Use Paypal Sandbox item in the Store Admin module.  I have also created a Sandbox account in PayPal.  When I Checkout, it takes me to the PayPal sandbox (primary URL).  However, once there, PayPal brings up a screen that says I have to login the use the Sandbox.  I was expecting that it would asking me to confirm my order, provide CC information, etc.  - that is, I was expecting all of my purchase information to be sent to PayPal.  If I'm supposed to "login", I have no idea what account to use.  I've tried various PayPal test accounts (buyer and seller).  However, once I've logged in, there's no evidence of the purchase coming from the DNN side.  Can anyone tell me what I'm missing 

Just figured this out myself yesturday.  I was having the same problem.    Turns'out that you have to logon to the sandbox main account prior to doing any testing through your website. I do it in a separate browser. This sets up the sandbox and makes it ready to accept your test transaction.

Here's a tip...When you get to the point where you need to enter the buyer's user id, go to the browser window where the main account is loged-in (as described above), then copy the user id. Go back to your transaction browser and paste it in.

Hope it helps...

-steve

Could you guys post a Step By Step guide?