Why Can't my Xbox App on my surface recognize the microphone?

[Windows Central Question]

Hi there,
I bought 2 surfaces for daughters for Christmas.
They both like playing Minecraft and want to record their gameplay for Youtube.

I can only record voice on 1 Surface though...

If I go into the Xbox DVR options, 1 shows Audio and Microphone options for ON/OFF
The other shows ONLY the Audio ON/OFF

They are both the exact same version of both Windows 10 and the same version of XBOX APP.
Both were installed on Christmas day this year.

Please help!

Thanks!