iOS Mail S/MIME cert installed and trusted but “No valid certificates found”

Yeah, unfortunately IdenTrust is no help, as I have A) done their installation correctly and B) their install procedure is the same as any SSL cert with Macs (into the KeyChain, export from Key Store, email the crts.) worked fine with iOS 15 and 16, until I restored-as-a-new-phone. Something in a new 16.2 environment is different than it was before, and it doesn't seem to have to do with trust. I could load and use even untrusted certs for signing before the reformat, iOS Mail didn't care beyond warning me. My situation is probably rare because nobody starts with a fresh install of iOS 16.2 if they can at all help it, they upgrade in place or they pull in an iCloud backup with their previous settings. I wonder if 3rd party certs are included in an iCloud backup?

Thanks for the clarification that 3rd-party certs would not be stored in an iCloud backup for restore, good to know.

Retail S/MIME certs, well there's just not much to them, as long as they are properly formatted, contain the values you need, are valid and hopefully trusted, there's not much to administration and there's no insight the cert vendor can make that isn't already contained within the cert. My certs were known-good when installed into iOS 15. They are not recognized in a freshly reformatted iOS16.2 environment, and iOS is the only variable. I get that there's little to no data available yet for the install of certs into vanilla 16.2, for instance it could be that the certs are fine but that the problem is with my configured Gmail accounts....with iOS Mail using OAuth I don't get to specify any Gmail settings, it's auto-configured. I am hoping someone else with this issue finds this thread. As my latest Apple Genius pointed out, many bugs absolutely don't exist until more than a few people show up to complain. Then it gets on someone's to-do list. Thanks again!