Dear ming jiang
Thanks for reaching out! Welcome to Microsoft Q&A. I'm Haien from Microsoft Q&A.
I understand that your Windows 11 system is no longer connecting to or even searching for Bluetooth devices. You've confirmed that the issue is not with the device itself, as it can connect to another PC, and you also noted that the problem appeared suddenly, even without a recent system update. That’s really puzzling, especially since you haven’t updated the system recently. I’m here to help you get this sorted out!
Solution 1: Restart Bluetooth Services
Press Windows Key + R to open the Run dialog > Type services.msc and press Enter > In the Services window, find the "Bluetooth Support Service." > Right-click on it and select "Restart." > Ensure "Startup type" is "Automatic" if it’s stopped. Repeat this process for any other Bluetooth-related services you find in the list > Restart your PC and try to connect your Bluetooth device again.
Solution 2: Use the Bluetooth Troubleshooter
Go to Settings (Windows Key + I) > Select "System" > "Troubleshoot." > Click on "Other troubleshooters." > Find "Bluetooth" in the list > click "Run." > Follow the on-screen instructions and see if the troubleshooter can find and fix the problem.
Solution 3: Check and Adjust Power Management Settings
Right-click the Start button > select "Device Manager." > Expand the "Bluetooth" category and double-click your Bluetooth adapter > Right-click on the adapter and select "Update driver". If it does not work, select "Uninstall device." > Go to the "Power Management" tab > Uncheck the box that says, "Allow the computer to turn off this device to save power." > Click OK > restart your PC.
For additional information, please visit this article: Fix Bluetooth problems in Windows - Microsoft Support
Solution 4: Perform a clean installation (if needed) OR Download the latest stable Windows 11 ISO
When using Insider Preview, please note that this is pre-release software and may have potential bugs or incompatibilities. While Microsoft is always working to fix download issues, overall stability can be more unpredictable than a stable release. Therefore, if none of the above solutions work, please consider these 2 options:
Install the latest Windows 11 Insider (if necessary)
Download the latest Windows 11 stable ISO
Options 1: Download the latest Windows 11 stable ISO
Download the latest stable Windows 11 ISO via this link: Download Windows 11
Once downloaded, right-click the ISO file > select "Mount." > On a virtual DVD drive > Run the setup.exe file from the mounted drive > Follow the on-screen prompts > choose "Keep personal files and apps." After the repair upgrade is complete and your system is stable > re-enroll in the Insider Program and try downloading the preview build again.
Options 2: Install the latest Windows 11 Insider (if necessary)
Download Windows 11 Insider via this link: Download Windows Insider Preview ISO > Create a bootable USB using the Media Creation Tool > Follow the on-screen instructions to join the Insider Program again.
Disclaimer: Please ensure that you backup any important data, including Documents, Pictures, Videos, and more to prevent unexpected error or missing important data via this additional article: How to back up and restore the registry in Windows - Microsoft Support.
Recommendation: Report to Feedback Hub
If none of the above solutions work, I strongly recommend that you contact Microsoft Support and submit feedback regarding your issue so they can verify your error.
Open the Feedback Hub app > Click "Add new feedback." > Provide a detailed description of the issue, including when it started, what you've tried, and the result > Submit the feedback under the suitable category.
For additional information about how to send feedback to Microsoft about payments/purchase, please visit this article to know more: Send feedback to Microsoft with the Feedback Hub app - Microsoft Support
If you've already tried these steps and are still encountering issues, please reply to this thread with the requested details so we can investigate further and ensure your subscription is activated properly. Also, please keep me updated with anything new that you were try to each option.
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We appreciate your patience and look forward to resolving this quickly for you.
Warm regards,
Haien - MSFT | Microsoft Q&A Support Specialist