The URL the customer will be redirected to upon a transaction being successful.
You can set in the 2 ways:
1. Dynamically (SuccessURL)
«AlphaHPP» → «Paypage Request Reference» → «Request a Paypage Session»
2. Statically («Success URL»)
My Magento 2 extension sets SuccessURL in the dynamic way, and your statically set value will be ignored.