I follow a principle known as HEAT:
Hear them out and let them vent
Empathize, let them know you understand
Apologize, and assure them it will work out
Take action, move on the issue with full intent
The 1st 3 calm them down, the last method shows your serious about taking care of the issue.
These work, I have used them most of my career with success.
Hope all works out.