@ PHITEK - I just tested your code and it work perfectly. I have the RS232 module plugged into Socket 6 (COM3) and I am receiving the data on the PC using TeraTerm.
Can you double check the firmware version that you have loaded, it should show 188.8.131.52 on the LCD display (this is not the correct version number, but at least you will be sure it is the latest )
EDIT: Ignore my question regarding the version, I read your initial post and it seems you do have the latest… Sorry about that.
As a side note and I am sure you are aware, but it is worth mentioning just in case. You should not allocate the byte array of 100 bytes as in the following code
byte sendBuffer = new byte;
Because the next line
sendBuffer = enc.GetBytes("Hello World from G400-D SoC");
Returns a new byte array with the data from GetBytes, so the initial byte array of 100 bytes is orphaned and is left to the GC to clean-up.
This is not causing your problem however…