This is a few months old but I recently opened a TAC case about this behavior. I could login to Presence but the Softphone was unregistered when connecting via VMWare View client (through an ASA 5500 in my environment).
I was told "the only client supported with the ASA is AnyConnect, so your PCOIP with Horizon View is not supportable"
I asked for clarification on why the local client networking was involved in the registration when I expect only hardware pass-through and was told the following...
"when working with an ASA, AnyConnect is designed to allow proper pass-through and handling of all protocols with the ASA. Another software package may or may not work with the ASA, but all protocols and data handlers may not be processed properly because we don’t know how the guys who wrote PCOIP with Horizon View."
I tested with AnyConnect and the softphone registered. Although it wasn't the best explanation, the bottom line is it unfortunately won't work. I'm looking into implementing an Expressway for this functionality.