I just did mine manually...
From the passenger side, look down at the center latch by the seatbelt you just mentioned.
You see the round pin at the forward part of the latch? Under and just to the rear of that pin is the latch lock. To the rear of the latch lock is the spring loaded piece that releases the latch lock or holds the latch lock. I pushed the spring loaded piece down with a small screwdriver which released the latch lock and let that side of the seat down. I'm guessing the seat release you normally use is releasing the driver side ok.