Hi James,
There is only one version of each plugin, which runs identically on all platforms. However, some plugins may require more recent versions of Icy itself to install, this could be one of your issues.
I would therefore suggest first to check whether you have the latest version of Icy (1.6.1.1 as of this email).
If you go to the “i” button next to the search bar, and click “Check for update”, you will see 2 activity bars at the bottom of your screen: The first one will look for updates to the Icy kernel (and will display “some updates are available…” if any, or “No application update available” if not). The second one will look for plugin updates suitable for the currently running kernel (i.e. not necessarily the most recent one), and let you install them as well.
To sum up, if you do see kernel updates, install them first (Icy will need to restart), then plugins should update automatically after restart. If you do not see any kernel (nor plugin) update, then get back to us so that we can investigate further.
Cheers
Alexandre