Sony WF-1000XM4 Manual page 41

If pairing is not established within 5 minutes, pairing mode is canceled. In this case, set the headset into the charging case, and
start the operation again from step 1.
Once Bluetooth devices are paired, there is no need to pair them again, except in the following cases:
Pairing information has been deleted after repair, etc.
When a 9th device is paired.
The headset can be paired with up to 8 devices. If a new device is paired after 8 devices are already paired, the registration
information of the paired device with the oldest connection date is overwritten with the information for the new device.
When the pairing information for the headset has been deleted from the Bluetooth device.
When the headset is initialized.
All of the pairing information is deleted. In this case, delete the pairing information for the headset from the connected device
and then pair them again.
The headset can be paired with multiple devices, but can only play music from 1 paired device at a time.
Related Topic
Wearing the headset
How to make a wireless connection to Bluetooth devices
Connecting to a paired iPhone
Listening to music from a device via Bluetooth connection
Disconnecting Bluetooth connection (after use)
Initializing the headset to restore factory settings
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