3/24 Note: What's also reported to work lately is the fix in the Comments section below from md zaid. There are other fixes to try in the Comments section if the numbered fixes below don't help.
1) Try these fixes for Bluetooth disappearing in Windows 11:
https://windowsreport.com/bluetooth-missing-device-manager-windows-11/ (Avoid ad links which intrude into editorial copy, especially avoid Restoro, PC Repair Tool and Reimage ads)
https://www.makeuseof.com/windows-11-missing-bluetooth/
https://www.guidingtech.com/ways-to-fix-bluetooth-missing-from-device-manager-in-windows-11/
https://thegeekpage.com/fix-windows-10-bluetooth-missing-solved/
https://helpdeskgeek.com/help-desk/fix-windows-11-10-bluetooth-missing/
https://pureinfotech.com/fix-missing-bluetooth-settings-windows-11/
https://www.youtube.com/watch?v=qrHmXuX2_uk
2) Reinstall the Bluetooth driver from the PC maker's Support Downloads webpage for your exact model. While there make sure that you also have the latest chipset, BIOS, display, network, bluetooth, USB and all other drivers, compared to the ones presently installed in Device Manager reached by right clicking the Start button. Some of these other drivers like Chipset and BIOS enable the Bluetooth driver.
Right click Start button to access Device Manager, locate Bluetooth device (if necessary from View tab Show Hidden Devices), on Driver tab see if Roll Back is available, if not try Update Driver, first automatically, then Browse, then Let Me Pick to try all previously installed Drivers.
If these fail Uninstall the Driver, restart PC to reinstall. If the BT driver is not there, access the View tab in Device Manager to "Show Hidden Devices."
Disable and then re-enable USB Root Hub (USB 3.0) in Device Manager (Courtesy Case Bell in Comments section 1/25/24)
3) See if you can System Restore to a point before the problem started: https://itechhacks.com/system-restore-windows-11/
System Restore is your first line of defense and can take you back to a point before a problem began like a time machine. If it doesn't help then you can undo it. Read about it first in the tutorial above and then try restoring to just before this started. If System Restore is not enabled on C drive do that now so it's available in the future.
If the problem repeats or System Restore doesn't work then check which Windows Updates were installed at Settings > Update & Security > Windows Updates > Update History, uninstall them there or System Restore again, then immediately check for and block the Updates with the Hide Updates tool explained here: https://www.droidwin.com/how-to-stop-only-a-specific-update-from-installing-in-windows-11/
4) If you think the BT adapter has failed, you can replace it easily with a USB nano adapter like this one:
5) If none of those help go over Windows 11 with this Performance Checklist to try to find and fix problems: https://answers.microsoft.com/en-us/windows/forum/windows_11-performance/windows-11-performance-and-install-inegrity/4f020fd1-f08c-45a3-8a30-c112f1a0b29f
If you were referred here from another thread, please post back results in that thread. Otherwise you can ask questions and share information in the Comments section below, including any broken links.
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