MicroSD card MP3s are deleted/unplayable on Note 4
What about you try and format it on the tablet itself instead of formatting it elsewhere.

sdxc's I believe are catchy and not compatible with every hardware. While you did format it your Mac I have no idea what was the default allocation size of the cluster and the tablet might not like that.

Also check that the card is firmly inserted in its place.

But before anything else... Check that your Samsung Tab 4 actually supports 128Gb card since my guess is that it doesn't but only 64 - check their specs.

Cheers.