XAPK will not install

XAPK and APKS are a package split into several pieces. The phone's ordinary installer will not open that as one APK.

• Renaming .xapk to .apk does not work. Inside are the main package and extra pieces.
• Make one APK with a tool that joins the pieces, then install that.
• If you install only one piece, the app opens and closes at once.

Play itself sends split packages. An XAPK from outside is those pieces gathered into one file.