I know this sounds simple, but did you toggle the ais target display on? Did you look at the manual? AIS | Official OpenCPN Homepage
Some of your settings in OpenCpn could be off or there may be some type of wiring
What does your icon look like? Here is an excerpt from the OpenCpn manual:
AIS data port
Select your AIS input port in the Connection Tab. The AIS button in the ToolBar, appears different according to the following conditions.
AIS Alive. The default AIS button. This icon appears as soon as an AIS port is active in the tool-box. It is also the normal state with an AIS receiver working and with no targets of interest.
AIS Alive and Activity, a small green circle will illuminate in the lower right corner of the Ais buton. If there is at least one AIS message every 4 seconds, the light will remain illuminated.
AIS Suppressed. This icon indicates only that target suppression is activated in the AIS tab in the ToolBox. Referring to the picture above there are two sort of suppression:
* Suppress display of all moored/anchored targets, max speed specified in dialog.
* Suppress Alerts for moored/anchored targets.
This icon will be over-ridden with the AIS alarm
button if an alarm
is, or becomes, active according to the AIS tab alarms settings in the toolbox.
AIS Alarm. A target exist that raises the alarm as defined in the AIS tab in the ToolBox. It is the three settings "CPA Calculations", that rules if and when an alarm is raised.
AIS Disabled. No targets, if available, are shown on the screen
. This button toggles with the other buttons. For example, if the AIS alarm button is visible, click the button and it will change to the "AIS Disabled" button, and all targets, alarms etc, disappears from the display. Click again and the original button and AIS display comes back.