I have been recording without issues for a while. I was recording files and opened a new file to record and no recording sound was picking up (flatline). I opened old files and they play back ok. Audacity 2.1.3, Windows 7 laptop, USB microphone for recording. I re-installed Audacity, re-booted laptop several times, tried different USB ports, tried recording with the laptop internal mic which isn't picking up either, checked Control Panel sound settings. Any suggestions? Thanks.