First please triple check that the PCLINK serial board is plugged in correctly as it is possible to insert it incorrectly or off by a pin.

Generally speaking the issue here is that the customer/installer is using a DSC serial interface while today's computers use USB only - therefor a USB to Serial adapter is used.  Sadly they are not all created equal and some will work, while others will not.

We have found the Keyspan USA-19HS to be most compatible.

Make sure you set the DLS software to communicate on the correct COM port!

Also you will need to activate the connection through the keypad. Entering programming section 499 then installer code and 499 again.