Thanks for this screenshot. When you try clicking any of the hair types, do they appear? I haven't tested this on Android 14 since I don't own an Android 14 so maybe that's a factor. Here's what you can try:
Download modelcustomization file from Gamebanana or my Patreon page: https://gamebanana.com/mods/610962
Place the file in "Android/Data/com.Nivium.iiMiiMaker/files/", overwriting the one that's already there (If one is there) then restart iiMii Maker. See if that makes a difference. Also I apologize for getting back to you so late. I have been checking Itch.io everyday and have gotten no notification. I only saw it when I manually checked the comments of posts.