After inserting a NIC adapter and pressing the ATTN button to configure the adapter, if you press the ATTN button too soon after the LED stops blinking, you might see the following errors in system logs:
rcm_daemon[]: NET: usage (device-path) get link information failure.
In this case, the removal operation will fail, and the LED will remain on to indicate that the adapater is still powerered and cannot be removed.
Recovery: Wait one minute, then press the ATTN button again to enable the adapter to be removed.
Workaround: If the PCIE cards gets into the UNK (unknown) state, you could do a reboot as a work around to get the system to recognize the cards.