Steady tone from the TH9x transmitter?

On my 2-week old Iris+, my transmitter just started emitting a constant high-pitch tone when the battery is plugged into the Iris+. I actually think the tone (alarm?) is coming from the frSky DJT module on the transmitter.

I’ve installed new batteries in the transmitter and a fully charged battery in the Iris+. Even with the alarm sounding, the Iris+ will arm and thrust works (tested with no props). The RX and TX are binding.

What is this steady alarm and what should I do? I’ve researched in many places, but no answers so far. No replies (yet) from 3DR support or from the frSky support forum.

Thanks for any advice.

Are both white switches in the down position on the RF module? The should both be in the down position.

Yes. Everything was fine on the previous flight. The only thing that changed was I used a different PC for Mission Planner. Thanks for the help!