RS232 to USB writes in NI max but does not read

Hi,

I want to connect SR830 lock in amplifier with my computer to read output values from it. While connecting lock-in using RS232 to USB in NI Max, write command executes without any error but while giving read command, it gives timeout error before operation is completed. 

Similarly, in my labview program read command doesn't work  and therefore, the program completes while giving only 0 output all the time. 

I have tried changing the RS232 to USB cables and even tried in different computers.

It will be really helpful if someone can help.

Thanks,

Urvashi