I also have developed this fault on my 2012 Prius V Station Wagon. All connections are intact under the seat. What was the solution to your problem.
Using a capable scan tool, check for any trouble codes from the Occupant Classification System. Absent any trouble codes, view the Live Data for that system. There are four weight sensors at the four corners of the passenger seat cushion. See if any of those readings look unreasonable, or don't respond to added weight on the seat cushion. There's also a total weight reading. It should be around zero (between −15 and 15 pounds) when the car is level and nothing is on the seat. If it isn't, there is a zero-point calibration that can be done. Once the reading is right with nothing on the seat, it can be checked with 66 pounds of solid metal weight on the seat (using a nonsolid weight might give a reading that won't match the expected). The reading should be between 60 and 72 pounds. Sometimes the readings can be off if the seat rail mounting bolts were tightened in a way that has distorted the seat rails. You can loosen all those bolts and wiggle the seat rails/frame to try to get the holes lined up with no stress, tighten the bolts again, and try the calibration and sensitivity checks again.
