[ICA-HM120] Why did the screen be blank or very slow video after my audio was enabled.

Your connection to the device does not have enough bandwidth to support a higher frame rate for the streamed image size. Try reducing the video streaming size to 352x120 or 160x128 and/or disabling audio.
Audio will consume 32 kbps. Disable audio to improve video. Your Internet connection may not have enough bandwidth to support streaming audio from the device.