INSTALL_FAILED_UPDATE_INCOMPATIBLE on JaecooApp Update

Android only lets an app update over an older copy when both are signed with the same key. If the JaecooApp on the car was installed from another source, for example a copy shared in a group, the installer can’t update it and reports The old JaecooApp on the car can’t be updated in place.

Why the copies don’t match

Every JaecooApp release from the installer is signed with the same key. That is what lets a new version install over the old one, including the updates JaecooApp downloads by itself in System. A copy rebuilt or re-signed by someone else carries a different key, so to Android it is a different app that happens to have the same name. Android’s own wording for this is signatures do not match.

Fix: remove the old copy, then install

1. On the installer page, connect the car and press Uninstall app.
2. If it can’t be removed: on the car open JaecooApp → System → Device Owner permission → Revoke, then press Uninstall app again (details).
3. Press Install JaecooApp to install the current version.

From then on, JaecooApp updates itself in System, with no cable.

Avoid it next time

• Install JaecooApp only from the installer page, and update it from System → Check for Updates in the app.
• Don’t install JaecooApp APKs shared in chat groups or downloaded from other sites.
• If several people use the car, agree on one way of updating, so nobody installs a different copy over it.