Once I was summoned by someone and we were in Sen's Fortress. Then, he acted like he was fighting someone and died, but I could not see anyone.
A few days later I summoned someone in the Duke's Archieves, and then was invaded. I fought the invader and died, but my summon did not fight. He just stood there and watched me. When I asked him why he didn't attack, he said he could not see anyone and did not get an invasion message.
A few days later I summoned someone in the Duke's Archieves, and then was invaded. I fought the invader and died, but my summon did not fight. He just stood there and watched me. When I asked him why he didn't attack, he said he could not see anyone and did not get an invasion message.