The C519M Headphones Can't Connect to the Transmitter, what should I do?

Normally the headphones will auto reconnect with C51 adapter once you turn them on. If not, you may need to reconnect them manually like following:

Step 1: Please make sure that the C51 adapter has been plugged tightly into your audio souce. 

Step 2: Get the headphones into pairing mode

Turn the headphones OFF first. From off, press & hold the button until you see the LED indicator on the headphones start flashing RED & BLUE.

Step 3: Get the C51 adapter into pairing mode

Press & hold the black MFB on C51 until the LED starts flashing BLUE & WHITE.

Keep them close to each other. Both LEDs will turn SOLID BLUE once they’ve successfully connected.

Step 4: Lock the headphones with the C51 adapter

Double click MFB on C51. The LED indicator will turn LIGHT BLUE for a few seconds and switch back to SOLID BLUE. The headphone is now locked to the C51.