64gb Ultra / can't write

Hoping someone can help me out here. Just bought a Samsung Galaxy tab 3 with 8gb of memory. Since I plan on using this as a media player with my Rhapsody account I wanted to increase the memory with a 64gb Micro SDXC which I take is compatible. When I look at the storage it shows the sd card there with memory but it won’t let me add anything to it. When I try to save my rhapsody to that file it says “can’t write to that location”. Did I miss a step somewhere? Was I wrong with compatibility? Is it just a corrupted card somehow?

…From what I understand I need the case sensitive/exact path location in order to change the download location… hpw do I go about getting this?