I have noticed this since November with all different versions of WiiMC. When I try to turn the volume up or down on the Wii U using the WiiMote, the sound bar moves, but the volume does not change. It never changes. Same exact WiiMC on my Wii works just fine, just not on the Wii U. I do not know if anyone else has reported this error but it sure would be nice to have it fixed.
On another note, WiiMC is fantastic. I have been using it DAILY for many years and am more than happy with it’s normally stellar performance. Thanks to Tantric for all of his hard work. Throw a donation his way if you can, especially if you use it everyday like me!
I used WiiMC up until the video files I was getting wouldn’t play anymore because most of them are HD. I even bought a second Wii just to use with WiiMC. I used it for years, now I use a $35 Amazon Fire TV stick with Kodi installed.