User blog comment:Resura/Dark Souls connection issues/@comment-5632187-20140607012241

There are a few things you should make sure of before you attempt to connect:

1) Make sure you have Cross-Region Play allowed. This setting can be found in the Settings -> Game Options and then the 4th from the bottom setting.

2) Make sure the person who is summoning is a human. If they are in hollow form, even in the earliest stages of it, summoning will be disabled for them.

3) Make sure you're both online. I know this sounds silly but trust me it happens more than you may think where you were signed out without realizing it.

4) Make sure neither of you are in the Company of Champions covenant, as the covenant disables all forms of co op.

Hope this helps!