Can't Apply a Promotion Code to an Existing Domain

[ZeroGravity]

I have created a promotion code to give a 100% discount on every product/domain in the system. Going to use it when bartering services with clients. Under the Client Profile it shows in the Promotion Code drop-down on the Product/Services tab, but not on the Domains tab.

• Recurring is enabled, set to recur 1 time (If it's not set to recurring it doesn't appear in any drop-down).
• I have selected every product and domain in the Applies To field.
• Nothing is selected in the Requires field.
• Allow existing products is checked.
• Nothing is selected in Billing Cycles.
• No dates or maximum usages are set.

Can anyone suggest why it may not be appearing on the domains tab.

Thanks
Darren