Hello Sinchai | TA (Trainocate),
Before looking for a Bluetooth driver, could you check what Bluetooth device Windows is actually detecting?
In Device Manager, do you see:
- A Bluetooth section
- An Unknown device
- A device with a yellow warning icon under Other devices
If so, please open the device's Properties > Details tab and post the Hardware Ids value.
The ASUS 551LN was sold with different wireless/Bluetooth adapters depending on configuration, so the correct driver cannot be identified from the laptop model alone.
Also, since you mentioned Bluetooth worked on Windows 11 24H and stopped after moving to Windows 11 25H, please confirm the exact Windows build you are currently running (Settings > System > About).
With the Hardware IDs, we can determine the Bluetooth chipset and check whether a compatible driver is available.