That's not much info to go on.
People probably need to know your operating system, what version of cs5 your trying the plugin in (32 or 64 bit)
and what version the plugin is.
Did you run the installer or just copy the plugin over to cs5?
I'm working on Imac OS X 10.5.8
It's PS CS5.1 v12.1 x64
I ran the installer and get an error message that PS does not recognize this type of file
I know about the compatiblity but came across this little nugget...
Imagenomic plans free plug-in updates for CS5
Imagenomic will be providing FREE compatibility updates of its Plug-in Products (Portraiture, Noiseware and RealGrain) for Adobe Photoshop CS5. Furthermore, we will be providing a FREE update for registered users of the Portraiture Plug-in for Lightroom to ensure compatibility with Adobe Photoshop Lightroom 3… For Mac OS X: We will be releasing compatibility updates to make sure our Plug-in products are fully compatible with Photoshop CS5 in both 64 and 32 bit mode.
now just need to know how to make it happen...
Just as an aside, I'm running Imagenomic's Portraiture plug-in on a Win7 Pro 64Bit machine with Photoshop CS5 and it runs flawlessly.
I was recommended the product by one of my clients, I work in IT Sales, who runs a portrait business; they're running the software on iMacs with Mountain Lion, AFAIA, and Photoshop CS5, without a hitch... I'll ask if they're also using the Noiseware.
Carolyn, You need to manually tell PS to find it during the install. And Noiseware still is NOT compatible with 64 bit MAc OS. It runs fine on PC but the Mac side has not been released. NW5 is in the works.