Question about normalizing audio gain

[ginau74985195]

I am working on a project (Premier Elements 2018). A portion of the video is an interview with a woman.  It was originally a continuous audio/video recording, but I cut/edited it to remove long pauses. I am attempting to normalize the audio gain on each clip, but (as seen in the screen shot) the audio of one clip will respond appropriately when I hit normalize, but the audiowave of the very next clip will disappear when I hit normalize.  All clips are literally identical (from the same original recording) so I am confused as to why "normalize" causes the audiowaves on some tracks to literally disappear while it performs perfectly on other clips.