My wireless headphones were working great until about two weeks ago. Now when I try to connect to them via Bluetooth, the connection fails, every time, due to a

My wireless headphones were working great until about two weeks ago. Now when I try to connect to them via Bluetooth, the connection fails, every time, due to an "unknown problem" and I should "try again later". Fortunately the detachable 3.5mm jack still works.