Will do my best to expose and explain the details that cause me a bit of a struggle to setting up and running instance on OpenBravo ERP.
1. Payment Method cannot be added to Business Partner (Vendor):
The solution is basically that the Payment Method needs to be added to the Financial Account of the Organization; if this is not done, you will not be able to accept this Payment Method under this.
2. Cannot add Product to Sales Order:
It is a problem with the Price List and the products, I used the Price List and checked the "Sales Price List", and it worked.
3. Can not Execute Payment to Financial Account
Error: 'Execution Process not defined for the pair Financial Account - Payment Method.'