I'm the tester for Islandora JW Player for 7x.1.8
The Islandora instructions for downloading the JW Player library on this page:
points to a non-existent zip file to get the jwplayer library:
On the longtailvideo.com stie (now named https://www.jwplayer.com/) says that version 6 is no longer available. It offers only version 7, so will be trying to see I can get version 7 working, but I'm just a tester not a developer, so I don't know the implications of moving to the version. It seems like I would be doing more than just testing.