I'm using audacity 2.4.2 on windows 10.0 can't record live

I’ve attempted to record live using audacity but all I see is a flat line when recording or playing back. No sound during playback. I’d appreciate any help you might be able to provide.

Make sure you’ve selected the correct [u]Recording Device[/u].

Are you using the microphone built into your laptop or an external mic? If you are using an external mic, what mic and how is it connected?

Do you see audio devices in the drop down lists on the task bar?
Mine are just greyed out - I have reverted to 2.3.1 which works fine.