No longer getting 'buy' preview window in vendors

I posted this in Scripting Tips first, but I'm not getting any results there, and I really need to get some help with this, so I thought I'd try here.

I've been using Hiro's free vendor package for my shop-- specifically, the turnkey vendor with back and forward arrows. Never had a problem setting them up or using them until now. I recently tried setting up a new one and noticed that right clicking it won't bring up the 'buy' preview window; instead, I get 'pay' in the pie menu. I tried with an alt, and a friend tried it, and both got the same result.

I really prefer getting the preview window, so that customers can see the permissions of an item before buying. I'm just wondering, has anybody else noticed this change, or is it just me? Have I just forgotten something really obvious in the setup?

If anybody can tell me how to get the 'buy' preview window to come up again, or even suggest another vendor that'll let customers see permissions before buying, I'd appreciate it. I don't want to have to add signs on all the vendors listing permissions. Thanks!