Lexicon Recording Studio Owner's Manual page 22

Recording Using the Microphone/Line Input
3. In the Inspector, click the IN: box and select IN 1 or IN 2 for the track input
4. In the Track 1 window, the Record Enable button
source. (IN 1 relates to Line 1/Inst, IN 2 relates to Line 2/Mic inputs.)
If it isn't, click it so that it turns red.
22
should already be red.