I am trying to integrate paypal pro into a website but keep getting this error. I have made several attempts now to contact PayPal and their support is realy poor. I was just wondering if anyone else has come accross this problem and can advise any possible solution. Below is what I have done so far: I have purchased the paypal pro and have the service active on my account. Running the system in test status, I have tried to process some test transactions. Using there sandbox facility, i am able to set up a test account and process a test payment with a test buyer account. This only works for the paypal express option (using a paypal account). When i attempt to use the credit/debit card payment option through paypal i get this error: Invalid merchant information: 10501-This transaction cannot be processed due to an invalid merchant configuration. RESULT: 5 PNREF: E78P0EA6A2B5 RESPMSG: Invalid merchant information: 10501-This transaction cannot be processed due to an invalid merchant configuration. HOSTCODE: 10501 During my responses from paypal, in the test mode I was advised to create a business seller account and ensure an api signature was assigned to it. After doing this it still does not work. I still get the same error. I was then advised that in order to test the credit/debit card processing i need to be in live mode. So presuming i now have to run actual payments with realy small amounts, this is what i tried. Again the paypal express payment option works fine, but the credit/debit card payment option fails again. Ive looked at a few forums and documentation, but i havent found a solution that works yet. I have also just had response back from paypal to say: "API credentials have been generated for you and are now enabled and ready to use". If anyone can advise, or give me any more details that would be great. Thanks Mark