Suddenly, minions stopped appearing.

Suddenly today, minions stopped appearing.
I tried turning them on and off on the spirit control screen, but they still didn't appear, and only one Infernal Hound remained.
Equipping and removing skill gems, and leaving and entering town didn't help.
When I removed the Infernal Hound passive skill, Infernal Hounds stopped appearing, but they remained in the skill slot and the support gem was still installed.