Why won't any of my Motorola smart phones connect to my Samsung S5 hotspot?

[AC Question]

Only my Motorola phones (MotoE 2015, MotoG, Razr Maxxx) have this issue. My tablets (Fire HDX, Nexus 7, HP TouchPad), smartphones (Samsung S3, Note 2, Note4), and laptops (Toshiba Satellite E45t and Dell M4700) are able to connect without any problems. The Motorola phones don't even see the hotspot (i.e. - scan does not see the S5 ssid) but can see all other WIFI ssids at home and work.