To install firmware on your A20 and Transmitter please go to the website below:
Astrogaming.com/software
Open up the ASTRO Command Center on your Computer.
Connect your Transmitter to your PC via the USB power cable. Plug your A20 headset into the Transmitter as if it were charging.
Now that you are hooked up to the PC, and your headset is connected, the ASTRO Command Center will prompt you to update your firmware for both the headset and the Transmitter.
Click on the link within the ASTRO Command Center for the firmware and hit “Download”.
If you have any issues, please contact support at https://www.astrogaming.com/contact/