myPlayer.play() expects an integer value, but when you read from the cookie you get a string. So to fix your problem, just pass the value through parseInt(), like this:
myPlayer.play(parseInt(playnow));
You will notice that on page reload, the proper track will be selected in the playlist as it starts playing, and it will continue to the next track correctly.
Demo: http://jsfiddle.net/alan0xd7/6kx616hr/1/
By the way, I think setInterval with 1 (1 millisecond) is too much, maybe 1000 (1 second) is enough.
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solved How to save current playing song in cookie?