Samsung Galaxy S5 - unable to encrypt (Verizon, 6.0.1)

[mcgonigiggle]

I've been thinking about enabling full-device encryption on my Samsung Galaxy S5; I went to try it today, but for some odd reason it won't encrypt at all (as far as I can tell). I went to Settings > Security > Protect Encrypted Data > Enter my password (meets complexity requirements) > Encrypt Phone. My phone then says "Encrypting..." for a few seconds, goes dark and finally restarts like normal. I'm honestly at a loss as to what else I can do to encrypt my phone. Any ideas? I'm currently running Android 6.0.1 on my Verizon Galaxy S5 (model SM-G900V).