It looks like you are trying to use our Demo account with another bank than the one valid for demo purposes.
If you want to try the Bank Data Conversion Service in Microsoft Dynamics NAV, you are able to do this by using the demouser account. In order for you to create a payment file you need to use the bank account called WWB-TRANSFERS and set it up to be using the bank called Demo Bank GB and choose BANKDATACONVSERVCT as the payment export format.
To export a real bank-file please follow the instructional video Subscribe to the AMC Bank Data Conversion Service here.
Remember that the first bank account you use is free of charge, so feel free to try the service with a real user.
Do you need some help, you can always raise a support case here