The playlist.m3u8 file is not available most probably because the HLS segmenter has stopped working. The HLS segmenter stops working when the stream is unpublished from your Wowza server.
It is possible that during the application restart, the encoder stream is being published again and that's why the segmenter starts working and the playlist.m3u8 is available for download.
The only way to know for sure is to take a look at your log files. Can you please send a ZIP archive containing your Wowza configuration and log files to
firstname.lastname@example.org so we can take a closer look.
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