monitoring 6221 and 2182a using labview

Two devices 6221 and 2182a are connected, I want to perform Delta measurement by using labview , I use Ethernet port for monitoring, when I run Labview, it can recognize 6221, but it gives an error that it could not recognize 2182a and says check that two devices connected correctly , But well, I connected these two devices together and I am absolutely sure that they are connected , I checked everything again but could not find the problem

Before using Labview or any other software, try just manual operation by pressing the Delta button on the 6221.
Reboot both.  Press Delta button and accept the default parameter values.  Press TRIG button when prompted.
Can that succeed?

Common pitfalls:
the RS-232 cable needs to be of type null modem.  That is the type we ship with 6221/2182A.

On both the 2182A and the 6221, configure the RS-232 settings.
 (19.2k BAUD, Flow is XonXoff, Terminator is CR).

After setting RS-232 settings on 6221, make GPIB or LAN the active interface.  Otherwise you will see error +809.
 

Thanks a lot for your reply
yes i checked the manual operation and it succeed
I'll check the connection again