Board Thread:Dark Souls III/@comment-28349606-20160501031053/@comment-4511886-20160501075802

Do you have the password mechanic activated? It will block out summon signs that are not on the same password as you. You can tell that it's active by the icon, that looks like the Name-Engraved Ring, under your stamina bar.

To turn it off (and on) go to your options and under the fifth tab - I believe - there should be a text box you can write in. To disable the password, simply erase all characters and confirm the 'selection'.

Other than that, you may simply not be a Host of Embers, or - in the worst case scenario, you've gotten soft-banned.