I cannot uninstall the app because it's not installed.
I cleared the cache of all apps, reboot and tried again : no luck, install failed, it starts to install, stops a bit later, says : app not installed
Removerd everything and installed 15.4.10 with root folder 205 : installs without problems.
I will download both APK and root folder 207 ( maybe corrupt download ) and ty again.
Let you know.