This morning I went all out trying to correct the health code.

I started by deleting the mini-programs in both WeChat and AliPay.

Within WeChat I also cleared the cache.
Next step was to completely remove WeChat Pay as described earlier, and once again I cleared the cache.

Then I setup WeChat Pay again with my new passport number.

It forced me to add a bank card and would only accept the name as it's recorded at the bank, but it did store the new passport number in my real name verification.
Then I tried scanning the QR code.

It's still returning the old data with my old passport number.

If the program had truly been removed with all data deleted as WeChat claimed it should no know all the other information that is put in when registering the health app.

Any more suggestions on what to do next?

I don't think it works for foreigners in general in WeChat? For me, it only worked in Alipay in the end.

@Dan,
For me it's not working in either WeChat or AliPay.

Both apps return the screen with my old passport number.

I didn't except total success in WeChat since it still forces the name to match the bank card, but in AliPay I don't have a bank card and my name is entered as on the passport.
With all data supposedly deleted, neither one should be returning the screen with my old passport number.

Did you try clearing the 'data cache'? Try uninstalling Alipay and then reinstall.

Yup, did all that multiple times. Does AliPay have a data cache hidden somewhere?

Don't know. I've given up on trying to change the Healthcode. Ha.Ha.

I've never been able to get either the WeChat or the AliPay health codes to work. Alipay tells me the network is busy and to wait 60 seconds, then try again - an infinite loop.

WeChat is much more responsive and immediately tells me the network is busy and try again.

Futility.

I'll try to check Yereth's comments on updating my ID - but am reluctant to change anything as that might affect WeChat pay and AliPay.

I did follow Yereth’s comments, including the bit about deactivating WeChat Pay. I’ve since set it up again with my new passport number and have successfully transferred funds to another user, from my bank card, and in store purchase. I’ve never used AliPay for any purpose yet and had only hoped that it would be the solution to this health code issue.

Besides cache, I think some mobile apps sniff the SIM card and phone number your phone is using (sometime they have to ask permission to do so), and could link that with your old information in their cloud. In such cases clearing all data in your phone will not help.

Another example of this is how TikTok, the foreign market version of Douyin, fails to install if the phone is using Chinese SIM.

JanJal: Good point. Many apps require a range of permissions before they will even open, such as many of the bank apps here.

However, it appears Tencent, with many of their technologies, matches not only on your passport number but also on your name. As Western names appear in a different way in about every system available, name matching will almost certainly result in a non-match. It's also perfectly possible that the geographical information used to get us a green code (or a red code) is matched in a different way than the info that tells Tencent and Ali whether we have had our vaccinations yet.

Long story short, I was able to update my WeChat passport number by the method above, but did not get matching vaccination information in my health code. The Alipay health code updated just fine for me, but Alipay already had my new passport number.