Sorry, your license key isn't valid for this domain

Hi, I've searched the forum, but haven't found a solution to this problem. I'm setting up a dev website which is in a subfolder on our main server (https://twelveyardsout.com/development/melisande). I've installed Perch 3 and ran the server test, which passed ok. Everything seemed to work, but when I try to log in to Perch I get an error saying that the licence key isn't valid for the domain. I've added the above url as the staging and development domains but still can't login. I've made sure that the "https://" isn't included as suggested in another thread. Can anyone help?

Thanks.