IOError in RaspberryPi

[mntolia]

Hi,
I am trying out the EC Sensor on the PI but I keep getting this error:

Traceback (most recent call last):
  File "DFRobot_EC_Read.py", line 26, in <module>
    adc0 = ads1115.readVoltage(0)
  File "../DFRobot_ADS1115.py", line 142, in readVoltage
    self.setSingle()
  File "../DFRobot_ADS1115.py", line 110, in setSingle
    bus.write_i2c_block_data(addr_G, ADS1115_REG_POINTER_CONFIG, CONFIG_REG)
  File "/usr/local/lib/python2.7/dist-packages/smbus_cffi-0.5.1-py2.7-linux-armv7l.egg/smbus/util.py", line 59, in validator
    return fn(*args, **kwdefaults)
  File "/usr/local/lib/python2.7/dist-packages/smbus_cffi-0.5.1-py2.7-linux-armv7l.egg/smbus/smbus.py", line 275, in write_i2c_block_data
    raise IOError(ffi.errno)
IOError: 5

I ran the files in your installation instructions but still, this issue occurs.