1. Since Bluetooth device searching is an interactive process between a phone and a pair of earbuds, the phone side may have Bluetooth logic issues that hinder the search for Ear (a). This phenomenon is not an issue with the earbuds. You can try turning the phone's Bluetooth off and then on again, or restart the device and try searching again.
2. If the problem persists, place both earbuds in the charging case, close the lid, and wait for more than 30 seconds to allow the earbuds to reboot, or place them in the case and open the lid, then long-press the function key for more than 10 seconds to restore to factory settings before trying again.