2tb is most common cause 4tb + fat 32 drives that work are hard to find. My new 4tbs will not format for wii. My old WD 4tb works on wii.
Must be lucky then as the 4tb I bought for my Wii worked without issue and just for thrills I tested out the other 4tb drives I have that are fat32 formatted, 2 Seagate and 2 WD, all bought at differing times and all mains powered. These all worked without issue. Also tried a portable 4tb with a "Y" usb cable and that also worked.
If either of my 8tb were fat32 id try them to just for shits, but I would be surprised if they worked properly.
All my drives were bought from mainstream high street retailers so are nothing special.