"Wrong file type, please select again" when choosing a ringtone

I have a Nexus 5, all my ringtones and notification sounds returned to default, and when I try to set any file as a sound I get this message:

Wrong file type, please select again

I get the same message no matter what file type I choose, including the files that were my sounds until this morning. I tried to delete cache memory and reboot but that did nothing.