Hi i'm Jan, If none of the suggestion works and this just happen recently. Try the following suggestion.
Try to power reset the computer.
Shutdown the computer.
Remove all external devices, external storage, controllers, and other USB devices.
unplug the computer for 20 seconds
Press and hold the power button for 20-30 seconds to turn off
then plug your power adapter for 30 seconds
Plug the Ac adapter
Then power on your computer
Then try to search and pair again the earbuds. If that didnt work, try to factory reset the OnePlus Buds 4. Check the OnePlus Buds 4 instruction manual or support on how to power reset the OnePlus Buds 4. Then try to search and pair again to your computer.