Hi, thank you for contacting JustAnswer.com. My name is Russell. I will do my best to provide the right answer to your question.
Your iOS devices are on the current level of iOS.
But, the customer's or user's devices may have a different level of iOS, not quite current.
And there's a question also, as to where the pushed links are appearing, on the user's (or, your) Apple devices. Are they appearing in a web browser? if so, some may be Safari, and some may be Mozilla Firefox or some other browser, perhaps. Or a similar difference.
Please mention more details about the context of the pushed links on the Apple devices, and I will advise you more specifically if I can.
It may be that a different form of push, or different codes, might need to be implemented if there are two different appearance contexts, and the different form or codes might need to sense the context first and send as appropriate.