In basic terms, your website’s PayPal transactions aren’t being tracked properly in Google Analytics 4 (GA4), though the credit card ones are just fine. Despite the data being correctly passed to GA4 after a PayPal purchase, the tag that’s supposed to tell GA4 about it isn’t triggering. You’ve ruled out the common issue of referral exclusion so it’s a bit of a mystery, but you’re considering if the problem might be the sequence of events, like the data being ready before the tag can handle it due to users leaving your site to pay through PayPal.