WhatsApp for Samsung Galaxy Core Prime

WhatsApp ended support for older Android versions, and current builds no longer activate on Lollipop (Android 5.0/5.1), so the up-to-date app will not register or receive messages on the Core Prime's stock Android 5.1.1. Your practical options are limited: install an old WhatsApp APK that still launched on Lollipop (it works only until the servers cut it off and gets no security updates), or flash a custom ROM that raises the phone to a newer Android version. For reliable day-to-day messaging, the dependable fix is to move your number to a newer phone. See how others solved this on Reddit

Empty chats after a restore usually mean the backup is tied to a different Google account or phone number than the one you verified with, so WhatsApp creates the chat shells but finds no data to pull. Uninstall WhatsApp, reinstall it, and on the restore screen make sure you are signed into the exact Google account that holds the backup and are verifying the same number. If Drive still pulls nothing, check for a local backup on the phone: on Android 11 and newer these live in Android/media/com.whatsapp/WhatsApp/Databases (older phones use Internal storage/WhatsApp/Databases), and WhatsApp will offer to restore from the local file if one is present. See how others solved this on Reddit

Chats go missing during a switch when the Google Drive backup did not finish, or the phone number/Google account on the new device does not match the one that made the backup. Before moving, open WhatsApp on the old phone and force a fresh backup under Settings > Chats > Chat backup > Back Up, then on the new phone verify the same number and accept the restore prompt during setup. If you skipped that prompt, the only way back is to uninstall, reinstall, and restore again, since the offer to restore appears only during the initial verification. See how others solved this on Reddit

For a carrier (SIM) lock, the proper route is to contact the original carrier and request an unlock code once any contract is paid off; they provide a code you enter after inserting a SIM from another network. Be wary of random paid unlock services, as a phone this old attracts scams. If instead you are locked out by a forgotten screen PIN, remote PIN removal is no longer offered, so the reliable recovery is a factory reset from recovery mode (hold Volume Up + Home + Power), which erases the device; you can sign back in afterward with the Google account that was on the phone. See how others solved this on Reddit

The Core Prime shipped with a low-end quad-core chip and only about 1 GB of RAM, so by modern standards it struggles with current apps and lost most app support years ago. To squeeze a bit more life out of it, clear app caches via Settings > Storage, uninstall apps you do not use, and consider a factory reset to clear years of buildup. For an active line it is best kept as a backup or media device, since many chat and banking apps no longer support its Android version. See how others solved this on Reddit