Login and grab orders that are shipped. Compare delivery date (x). See if it changes or matches the estimate at time of order(y). If I package is deemed late create a message containing x and y and order number. Open chat support paste message. Might have to throw some additional canned responses but it seems pretty easy.
Paribus contacts customer service to Amazon on your behalf for missed packages. Literally they open a ticket with amazon and complain.[0]
[0]: https://paribus.co/support/topics/purchases-and-claims/274
I'll help test. :)
It's been a long while since they missed a prime delivery date for me, but the couple of times they did, they credited my account automatically without my involvement (other than reading their email notification). Maybe I just got lucky?
What's especially annoying is that you have to pro-actively reach out to them. This isn't customer-obsessed.