Adapter Not Connecting: "pipe error"

[allegedlymarco]

Issue encountered using a Mayflash controller adapter, after following the instructions to install WinUSB and ViGEmBus.
Attempted solutions: changing gcfeeder configurations, using a different version of gcfeeder, using drivers other than WinUSB, using different USB ports on the computer, changing the adapter to "PC" mode, plugging the adapter's other USB cable into the computer, running gcfeeder as Administrator, closing all applications besides gcfeeder, restarting the computer, and repairing/reinstalling the WinUSB and ViGEmBus drivers.
Screenshot of issue:

[Sirius902]

Interesting, the adapter should be working in Wii U mode. Have you tried updating the firmware on the Mayflash adapter? If that doesn't work would you mind trying to see if the adapter works on Dolphin with the GameCube Adapter for Wii U option with the adapter set to Wii U mode? If it works on Dolphin I may need to take a look at the Dolphin code again to see if anything has changed with how they handle GameCube adapters.