Invitation Code Settings Do Not Save

I have set up my invitation Code. I want it to apply to Retailer Membership. If I check the box for Retailer membership under Membership 2...Invitation Codes...merirtail...and press save...the check boxes default back to ALL and then when I test the membership registration for Retailer Membership it is not restricted to invite only.

Please advise.

(You have support access at present)