Allright, fist off, cIOSX 20 is not recommended in guides here, but I don't think that is the problem. It could be though. cIOS38 rev17 is recommended in most guides. You might want to give it a try.
Secondly, we will need a syscheck to see which IOS' are installed.
Furthermore, it would be helpful if we knew which loaders you are using and which version.
For the Mii channel: try to delete it using AnyTitle Deleter DB to completly remove it and the reinstall it using dop-mii. Also, you might want to check if the right IOS is onstalled for it.