You never replied about tank size, numbers of seahorses, and tank water temperature.
As for the dip, you take chlorine free water, and adjust the pH to be the same as what the tank water is, using an acid to lower the pH or a base to increase the pH. You also match the temperature to tank water.
Place the seahorse into the container of dip water and usually it will thrash around for a bit.
After that, it may lie on the bottom or it may continue slowly moving around.
If it lays on the bottom and won't show any response when you touch it, then remove it at that time. Otherwise, leave it for 12 minutes.
Place it back in the salt water after the dip.
You may have to start hand feeding if it doesn't start eating soon as seahorses that go more than 4 days without food are hard to get back to eating again, often leading to their death.
Are you sure the trigger is not stuck?