Can you walk me through the steps you did to try and install it? Are you on stock Android or Graphene? Did you download the mainnet or stagenet apk? Are you installing the latest version (v0.3.0)?

Do you already have Amethyst installed? There was an issue before where garnet could not be installed alongside Amethyst without using something like apk editor. Not sure if that's been fixed in (v0.3.0)