Problem reading Modbus/TCP with Instrument Control Toolbox

I am trying to read a Victron Energy photovoltaic system from Modbus/TCP (see the mapping example here) by means of the Instrument Control Toolbox. First, I created the object by means of this command:

 >>m = modbus('tcpip', '192.168.XXX.50', 502)

and it seems to respond correctly because the answer is:

m = 
  Modbus TCPIP with properties:
  DeviceAddress: '192.168.XXX.50'
  Port: 502
  Status: 'open'
  NumRetries: 1
  Timeout: 10 (seconds)
  ByteOrder: 'big-endian'
  WordOrder: 'big-endian'

Then, I try to read a register through the command read(m,target,address,count, serverId):

>> read(m,'holdingregs',3,1,246)

And I found the following error:

The Modbus server returned an invalid address error. Address + count is out of range.

How can I solve this problem?