Samsung Galaxy S21+ will not pair or stay connected over Bluetooth

The checks in more detail

The S21+'s Wi-Fi and Bluetooth share the 2.4 GHz band, so move to 5 GHz if audio stutters. A restart and a cache partition wipe after the final update help, and a network reset is the last software step. Cars with older software may not pair, so update the car. If the Bluetooth toggle is grayed out, the radio needs service. Use the Bluetooth diagnostic in Samsung Members to test the radio and quote the result to support.

If a headset works for music but not for calls on the S21+, check that Call audio is enabled for the device and that the phone's call app is not set to use the earpiece by default for that call. Owners also find that two devices connected at once, such as a watch and earbuds, can compete for the audio; disconnect one to test. Samsung's SmartThings Find and Nearby device scanning also use Bluetooth in the background, and some owners notice that turning Nearby device scanning off in Settings, Connections, More connection settings steadies headphones.

Try it for a day and see. Keep in mind that turning it off disables features such as quick sharing prompts, so turn it back on if the trade-off is not worth it. A habit that avoids many Bluetooth faults is naming each accessory distinctively in the Bluetooth list, so that you can tell your car from your friend's and your old headset from the new one, because a list full of devices named Headphones invites connecting to the wrong one. Keep a short list on this phone, remove devices you no longer own, and give the rest clear names.