I was checking the Plugin and the issues is a little more complex . it give link error because in Unreal 5.6 they did a few changes to the Curl implementation of the HTTP request, and now is not possible to access that class from outside directly , even with the hack the VoiceSDK use to access it is not linking anymore.
Good news is I refactored the class FWitHttpRequest to access all HTTP request through the proper interfaces (IHttpRequest) and (IHttpResponse) and is working now.
I tried the Unreal-VoiceSDK-Sample and I can turn the cube red with the MIC but after that doesnt want to get more voice commands.
The hard part is done , I just need a few days to test it a little more since I dont really know how this plugin work.
Well , looks like is working fine so far, you let me know.