[JohnM]

REW is fairly fussy about the shapes of response features it identifies as peaks. This is because it is targeting peaks due to modal resonances, as these are correctible using parametric EQ filters. Filters need to be accurately matched to the resonance they are correcting, otherwise they can do more harm than good. If you email me the .mdat file from your measurement I'll be happy to look at it and see whether REW should have identified a peak but didn't. You can manually add additional filters, REW will optimise them to match the response in the same way as filters REW applies itself to peaks it has identified.