No markers and Cluster Markers showing in the map from last fews weeks

[mdalamin706688]

Sir @csessig86 csessig86, Can you tell us how can we solve it and this map will run as like before very smoothly.. We waiting for your kind reply Sir
///Errors///
---> GEThttps://spreadsheets.google.com/feeds/worksheets/0As3JvOeYDO50dF9NWWRiaTdqNmdKQ1lCY3dpdDhZU3c/public/basic?alt=json

---> SyntaxError: JSON.parse: unexpected character at line 1 column 1 of the JSON data

---> Uncaught TypeError: data is undefined