How to debug certain e-mails not being received

I currently have random issues with Cloudflare’s Email Routing feature, where I never receive an Email from certain Websites, while the same Routed mail works on others.

A recent example I can give is PayPal, where adding a new mail, in my case a Email Route to my account should give me an Email to verify, but I never received one at all. The Route does work, given I have tested sending an Email to this Adress and it was properly forwarded.
Another example is Atlassian, where I never received any Email about updates or alike for a Ticket I made, causing said Ticket to be closed without any changes…

Is there any way for me to debug the Routing on CF, to see if there is an issue on their end? Could this perhaps be the Website blocking specific IP(-ranges), sadly including those used for my adress?

A quick update: The Email now was sent after a retry… So in this case (with paypal) was it most likely DNS not being up-to-date and taking a while to propagate to them… or something else.

This, however, doesn’t change the fact of the other case, where no Emails where received, despite the Email Adress existing for years at this point.