May I suggest an alternate methodology. Go to
VaxYes fill out the information from your "passport" wait a few hours for it to be verified then you will receive an email with an attachment that when clicked on will place a vaxination passport in the Wallet on your iPhones.
That's not an option for me as the download is from a secure government site here is Canada.
Anyway, on my wife's iPhone a file appeared immediately on her desktop but did not on mine. So, it seems to me, there must be a simple way to do it....that I am just unable to figure out.
Edit: In looking around elsewhere I have seen references to a Files App that should just be on the phone. I don't have one. Could that be part of the problem?