WhatsApp for OnePlus One

This is usually a battery-optimization or background-data block kicking in after the update. Go to Settings > Apps > WhatsApp > Battery and set it to "Don't optimize" (or "No restrictions" in OxygenOS), then under Data usage enable Background data and unrestricted data. Also confirm your date and time are set to Automatic, since a wrong clock breaks the SMS verification handshake. See how others solved this on Reddit

OnePlus's aggressive battery management is the usual cause, killing WhatsApp in the background. Open Settings > Battery > Battery optimization, find WhatsApp and choose "Don't optimize," then go to Settings > Apps > WhatsApp > Battery and enable "Allow background activity" and lock the app in Recents so it isn't cleared. Finally, make sure WhatsApp notifications are allowed under Settings > Apps > WhatsApp > Notifications. See how others solved this on Reddit

If both phones are Android, install WhatsApp on the OnePlus, verify the same number, and when prompted restore from Google Drive using the same Google account where your old phone backed up (check the old phone's Settings > Chats > Chat backup first). Alternatively use the built-in "Transfer chats" tool over a local QR-code scan, which doesn't need a cloud backup. The backup must be tied to the same Google account signed in on the OnePlus. See how others solved this on Reddit

Use WhatsApp's official iPhone-to-Android move, which needs a physical cable: connect the iPhone to the OnePlus with a USB-C to Lightning cable, then on the OnePlus start setup, choose "Transfer chats from iPhone," and scan the on-screen QR code with the iPhone's camera to begin. Keep both phones unlocked and connected throughout, and verify the same phone number on the OnePlus when prompted. The transfer is wired and direct, so an iCloud backup isn't used. See how others solved this on Reddit

This is almost always the phone's battery saver suspending WhatsApp while the screen is off. Go to Settings > Apps > WhatsApp > Battery, set "Don't optimize" / "No restrictions," and enable background activity, then lock WhatsApp in the Recents screen so OxygenOS won't kill it. Using WhatsApp's multi-device feature (Settings > Linked devices) also helps, since linked sessions stay active even if the phone briefly drops off. See how others solved this on Reddit

There's no built-in WhatsApp call recorder, and OnePlus's own call recorder only captures regular cellular calls, not VoIP audio from WhatsApp. The reliable workaround is to use the screen recorder from the Quick Settings panel with internal audio enabled, then start the WhatsApp call. Be aware that recording calls without the other person's consent may be illegal where you live, so check local rules first. See how others solved this on Reddit