It worked here, I have no more clues then. Someone else may be able to help you
Did you change the slider above? If you did reset it to the default 100 I think? Also mayflash adapters have lots of bugs, so make sure to get the later drivers.
As it turns out, the rumble works with Dolphin 4.0.2 but it does not work with the version of Dolphin I am using for netplay (dolphin-dc-netplay-4.0-652-x64)
Is there anyway to fix this issue with my version of Dolphin?
Also what should my threshold be set to?
You mean under the buttons? That is just for advanced stuff like using an analog for a button, 50 is fine unless it needs to be changed.