WhatsApp for Samsung Galaxy J7

WhatsApp has raised its minimum Android version over the years, and the oldest Galaxy J7 units shipped on Android 5.0/5.1 (Lollipop), which is no longer supported, so the app stops updating and eventually stops letting you log in. Check your version under Settings > About phone > Software information; if you're on Android 6.0 (Marshmallow) or higher you can usually keep using a current build, but on an unsupported version your only real fix is to move your account to a newer phone. Back up your chats first via WhatsApp > Settings > Chats > Chat backup to Google Drive before switching devices. See how others solved this on Reddit

This is almost always Android's battery optimization closing WhatsApp in the background. Go to Settings > Apps > WhatsApp > Battery and set it to Unrestricted (on older One UI it's Settings > Apps > WhatsApp > Battery > turn off optimization), then in WhatsApp > Settings > Notifications confirm that call notifications and the ringtone are enabled. Also make sure WhatsApp is allowed to run in the background so it can wake the phone for incoming calls. See how others solved this on Reddit

This means a modified or unofficial APK is installed (such as GB or FM WhatsApp), and the official servers refuse to let those accounts in. Uninstall that version, then install genuine WhatsApp from the Google Play Store and restore only from an official backup. If your account is temporarily blocked, you typically have to wait out the block and only sign back in from the legitimate app; switching to the official version is what eventually restores access, so avoid the modified builds going forward. See how others solved this on Reddit

WhatsApp compares your system clock to its servers, and an older Galaxy J7 can drift when network time fails to sync. Go to Settings > General management > Date and time and turn on Automatic date and time; if it's already on, toggle it off and back on, or set the correct date manually. Rebooting afterward forces a fresh time sync and usually clears the warning. See how others solved this on Reddit

When you verify your number on a new device, WhatsApp signs out the old one, so the copy on the Galaxy J7 becomes read-only and won't send or receive new messages. This is expected, because one number can only be active on one phone at a time (plus its linked companion devices). If you want to use the J7 again, you'd have to re-verify the number on it, but that will then deactivate the new phone. See how others solved this on Reddit

First confirm WhatsApp has microphone access under Settings > Apps > WhatsApp > Permissions > Microphone (set to Allow). If the permission is on but the mic still fails, test it in a voice recorder app to rule out a hardware fault, since the J7's mic opening can collect dust over the years and benefit from gentle cleaning. Removing any case or screen protector covering the bottom microphone, and turning off Bluetooth so audio isn't routed to another device, often restores call audio. See how others solved this on Reddit