Try to increase your app version in configuration xml file, AIR framework will think you've got a new version and will ask a user to upgrade, since upgrade is not so scary for the user, I think your boss will accept that
If the old certificate is still valid, you can use a migration signature with the ADT tool.
If the old cert has expired, then the uninstall/reinstall procedure is the only option.
When an AIR application is signed by a different certificate, it is considered a different application.
That is why you get the error message.
If your original certificate is still valid, use the certificate migration feature to sign the AIR file using ADT.
We have also encountered this error recently, as our original cert has expired and we need to support the auto-update process to a version which was signed with our replacement cert. We have literally 1000s of users on this application. What can be done to override this?
You should never let your certificate expire before renewing it or getting a new one.
Did you get a new certificate or renew the old one?
If new, then your users must uninstall the old version and then install your new version. Any data your apps stores in the EncryptedLocalStore will be inaccessible. Any files your application has stored in the application storage directory will have to be copied to the new storage directory by the updated app.
If you renewed the certificate, then presumably you are getting this error because the Certificate Authority has changed their own certificates used to sign their issued certs. If this is the case, they might (for some thousands of dollars) be willing to perform a key ceremony to bring the old certificate out of retirement and reissue your new certificate so that it has the same identity as the old one.