How to set up paid trial subscription with paypal

I have a paid trial subscription offer. I set it up by following the instructions here:

https://classic-infusionsoft.knowledgeowl.com/help/how-to-create-a-paid-trial-subscription

It works well with credit card payment. I recently applied for paypal reference transaction, hoping I can use both paypal and credit card to process recurring payments. But I have just noticed that the paid trial subscription I set up does not work with paypal.

I wonder if there is any other way to set up a paid trial subscription with paypal in infusionsoft.

Thank you very much for your help.

Hi, @Song_Chengxiang. It would only work with a PayPal Payflow account https://www.paypal.com/us/webapps/mpp/payflow-payment-gateway

Why would PayPal not work for this the same way that it works for regular (non-trial) subscriptions using reference transaction?