The Low Flow alert means that any flow at all was detected for a period of 2 hours. When that alert occurs, the flow has already been happening, and visually inspecting a meter wheel is not likely able to reveal the activity of a small leak. However, I am not sure how sensitive or obvious your utility meter displays activity.
If you are certain that no flow at all is actually occurring, a factory reset of the SWM150 can be tried.
Steps to remove it from your network then factory reset it are described in the link below: