Apple login "Hide my Email" does not forward emails

Hi there!

My wife has an iPhone 13 Pro (v16.3.1), and she used "Apple Login" to some webshops with its "Hide My Email" functionality. She got the ***@privaterelay.appleid.com address, and it says that emails will be forwarded to her ***@gmail.com address.

However, these emails (e.g., order confirmations, shipping details) has never arrived, which is a quite annoying. I used the same method with my 14 Pro (v16.3.1), and it works for me. I have double checked the forwarding settings, and already spoke with an employee from the support, but without any luck.

Do you have any ideas to try out?