Certification Discounts via ESI

Hi, 

I receive 100% discounts on taking Microsoft certifications as my company uses ESI, one particular exam (PL 600) isn't showing a voucher when I go to book, every other exam that I have tried does. Not sure if this is whether its recently been released but would appreciate any help figuring out how I can book it with the discount, I have tried clearing cookies\using a different machine just in case that helps without any luck.

Thanks,

Dale