According your explanation you don't miss something, the SSD interface of Pc Lap counter is running and the led is green and you set a race by clicking on "new race" button and start it by clicking on the "start" button or by pushing the "start" button of the powerbase.
1. Maybe you don't put drivers on good lanes, i mean car#1 on lane#1 , car#2 on lane#2, etc...? (see print screen below)
2. Is there any message in the message part of Pc Lap counter like "lap rejected..." ?
3. Is there any message in the SSD interface of Pc Lap Counter like "COM1 error..." ?
4. Did you changed the display settings of Pc Lap Counter ? , maybe you set the text color same as the background color ? (in the display setting window you can load the default display by clicking on the "Open" button).
5. What happend when you simulate laps by using the Keyboard ?
6. Which version of Pc Lap Counter do you use ?