Not ALL COE parks accept the card.
Some, not many, COE parks are operated by independent contractors and they may or may offer the full discount, a partial discount, or no discount at all.
I understand this also may be the case in smaller National Parks, but have been unable to confirm it.
Camping Rig: 2006 Outback 27 RSDS--
2005 Dodge 3500 - Dually- Cummins
Full time since June 2006