On the Cadence server, near grid P25, my character Mallorin was aggro'd by a venerable goblin. I was within ten tiles of a guard tower. There was a tower guard closer to me than ten tiles. I typed "Guards" in local. I got no response any tower guard, and no text response in any chat window. I then typed "Help" in local and there was no response. I pulled the mob closer to the guard tower and continues to alternate between help and guards. There was never any response. The entire time the goblin was selected as my attack target.
What I did was call for guards.
What I expected was for a guard to engage my active target.
What happened was that no guards came to assist, even though one was less than ten tiles away, and so was a guard tower.
This happened on a deed called Brasschaat Harbour on the Cadence server.
I escaped the goblin by going into the water, and I asked about it in the CA HELP chat. I did not personally test this for repeatability, but after I provided details, Baeowuf told me it had been repeated and that I should submit it as a bug report.