Make sure the APEX 2800 is in a proper x8/x16 PCI-e slot. There are different combinations of ways to enable/change PCI-e lanes from say x8 to x4 depending on your configuration.
In most cases, when an error shows up in putty (OUT_OF_Service) make sure the PCI-e slot is properly configured to support x8/x16 for the APEX 2800 to function properly.
Check with your motherboard manufacture for further details.
Here is an example of a APEX2800 driver/device summary reports in Putty when properly connected: