It's more likely that the card isn't supported. Check this VMDirectPath Tech Note for more information on supported devices.
Good Luck!
Brian Atkinson | vExpert | VMTN Moderator | Author of "VCP5-DCV VMware Certified Professional-Data Center Virtualization on vSphere 5.5 Study Guide: VCP-550" | @vmroyale | http://vmroyale.com