Although I rarely use this feature anymore I did notice that Paypal is no longer providing Tokens to put into the Web Form Builder. Upon some checking in the Paypal forums they suggest using that the process is out of date. I would assume payment cannot be processed from the form any longer.
PDT is completely unreliable, because returns are never guaranteed to happen, due to browser/network crashes or the customer not waiting for the auto-return (there is a timer) or not clicking through to return (typically guests w/o an account must be shown a receipt and click to return). So PDT is suitable for informational purposes only (e.g. showing buyers a thank you message when they do return.).
Absolutely no business logic should depend on a PDT return actually occurring. Instead, if you need a dependable notification from PayPal of payment completion, an asynchronous IPN or one of the newer webhooks should be listened for -- or alternatively, the integration should be changed to a more robust synchronous server-side one such as this pattern: https://developer.paypal.com/demo/check … ern/server , where there is always an immediate API response on payment capture for notification purposes.
TL;DR it's a super old web 1.0 thing and nearly worthless in 2020.. still around for backwards compatibility, not because it makes sense to use.
https://www.youtube.com/channel/UCL8qVv … ttneYaMSJA