Code not working

I have written the following code to log accelerometer values to a CSV file.

var ruuvi = require(“Ruuvitag”);
var st = require(“Storage”);
const length = 500;
var myFile = st.open(“data.csv”,“a”);
var j = 0;
ruuvi.setAccelOn(true);
ruuvi.accel.setPowerMode(“normal”);

for( var i=0; i<length; i++) {
var line = ruuvi.accel.getXYZ();
if(line.new == true) {
var a = j+1 + ‘,’ + line.x + ‘,’ + line.y + ‘,’ + line.z + ‘\n’;
j++;
myFile.write(a);
}
}
ruuvi.setAccelOn(false);

//setTimeout(“print(process.memory());”, 1);

I keep getting this error…

Uncaught Error: Unable to find or create file
at line 25 col 19
myFile.write(b);

There’s nothing that would erase old files, my guess is that there’s no more space in flash.