I ran into the same thing last week. Although it wasn't just Alti-verb properties, it was purely anything in the Wwise convolution verb. As soon as anything was changed or another impulse was loaded the plug-in would completely cease to function in game until I generated the sound banks again. I am guessing because the impulses and their changes need to be re-generated to function in runtime just like trying to switch out a SFX in real time doesn't work?
This is direct from the User Guide, but I would like to hear why changing parameters don't function in realtime: "Some effects, such as the Convolution Reverb, require media files to work. For
example, the Convolution Reverb requires an impulse response file as its plugin
media. Those plug-in media files need to be included inside a SoundBank
for the effect to function normally in the game. You also need to make sure the
SoundBanks containing the media files are loaded at the moment you need the
effect to be instantiated."