I've always used m-audio 2x2 for external sound card because it converts my mic input signal to digital. Just upgraded from Vegas 8 to Vegas 20 and get this message:
I have an M-Audio M-Track which has recorded well in many versions of Vegas Pro (since 2016 anyway). Audio sample rate has always been selectable in Windows/Control Panel/Manage Audio Devices/Recording (tab).
BTW, no distinction between audio and video was given in the original post - hence the confusion.
What is your m audio set to? Is the sample rate the same as your Vegas project? Maybe Vegas cannot change the sample rate of the audio interface. I had this happen with usb sound card.