Why do some plugins work and others don't?

I have been using Choir from Kompose in Soundbox with no issues.

I bought another of their plugins called Somara today to keep things interesting.

However despite doing all the things I can think of the new plugin does not work.

How can this be?

No matter how hard I try to get it to activate it is permanently stuck on the Choir plugin. It is like it has not downloaded into Soundbox properly or something. I have tried deleting it and downloading it several times.

Hi, are you using the latest 1.0.7 version of Soundbox?