Can't create more than 3 Subscriptions?! WHY!!?

Hey guys,

So I've installed membership. I have 2 levels - one for "Visitors" who are non logged in members. I have another, which is "Full Access" so you get TOTAL access. However, I need to create 4 subscription levels as our membership fees are a donation/range amount. Ie, $250 py / $500 py / $1000 py / $5000 py - At the moment I am only able to add 3 types. Then the add new button disappears. What the heck?

Can someone get in touch asap, this is ridiculous.