I think you hit the API limit for the day. Maybe you have lots of coins or maybe your timer is set very frequently. I have about 45 coins and call UPDATE every 10 minutes. I didn't encounter error with my settings. If you have 30+ coins, the script tries to get top 100 listing and uses the results. You could try changing "var useBatchRequestThreshold = 30;". If you coins are mostly in top 100 it will reduce your API call (urlfetch). Try to set it to lower than number of coins.

You'll have to wait to have the error go away.