In some cases, the pocketwatch will not raise when approaching certain obviously-dead corpses.
There was a bug related to this issue in "The Calling" chapter that was fixed in version 1.0.92.
In other cases, commonly in the "Soldiers of the Sea" chapter, the watch is not raising because you're currently within a flashback and the corpse's death has not been visited yet.
To progress, find this same corpse while not within any flashbacks, on the 1807 ship. It may or may not be in the same location - at some point you followed a ghost trail to reveal the corpse. When you approach the blurry corpse on the 1807 ship, the watch will raise but remain closed. This is an indication that you have not visited the death flashback yet.