Microphone won't show up

Hello. I am brand new to recording but I really want to see what I can with some stuff that i’ve written. I have a scarlett 2i4 audio interface and microphone which has worked well in the past, but for some reason Ardour isn’t picking it up when I plug it in. At the beginning of my session when I plug it into my computer it will show up for a second and then disappear. I am not sure the reason for this. Also once I open my session I cannot figure out how to switch recording devices. It’s using my built in microphone on the computer which obviously isn’t going to work. Any help would be appreciated.

What OS are you on? It sounds like whatever audio system you are using is not configured completely correct.