I can think of a handful of reasons that an electric seat might stop working (based on my painfully thorough history with the one in my Jeep Grand Cherokee). Let's go in order of simplest to diagnose and deal with:
1.) Fuse: Ideally, a fuse should only blow when something has gone wrong. It is there to protect other, more expensive components from burning up due to high current (or starting a fire). However, in my Jeep, the mechanism that physically moved required lithium grease. And no one had greased it since it had left the factory. Over the years, moisture, rust, sand, dog hair, etc. built up and increased the drag. And, the harder the motor had to work, the higher the current went. When a motor is first powered on, it is basically a dead short. Once it starts moving, the internal resistance goes up sharply. So, if the motor isn't able to spin [enough], the current will rise. If you do have a blown fuse, simply replacing it will probably only help temporarily. Make sure nothing is obstructing movement (aluminum cans, 20 Oz. plastic bottles, tools, etc...I've seen me do it). Also, if you have heated seats, you may have more than one fuse with the word "seat" in the name. Make sure you are looking at the right one.
2.) Switch: I don't know why no one can make a switch that lasts. And different switches have different behavior. For example, I've had window switches that stopped working in a single direction (i.e. would go down but not up). And I've had switches that just stopped working altogether. If the passenger side has the same type a switch, swapping them temporarily is a fairly quick test. Alternately, you can use a multi-meter to test for continuity when the switch is moved. If the seat has suddenly stopped moving in every possible direction at once, it is less likely that it is a single switch.
3.) Loose connector brick: After I replaced the entire mechanism under my driver's seat (because it had slowly broken in 3 of the 4 main places), I apparently did not push the lego-style connector back on hard enough for it to lock. So, over time, it vibrated loose enough to stop making contact. When that happened, ALL of the seat functionality went at once. Unless you, or someone else, has messed with that, it's pretty unlikely to have come loose. In fact, getting it off was kind of a pain.
4.) Bad motor: I have never actually had this happen on a seat. However, it's not terribly different from a window motor, and I've had lots of those go bad. The seat motor is a bit beefier as it has to move a human weighing in the hundreds of pounds instead of a single piece of glass. And a gearbox helps. My seat actually had two separate motors for different types of movement. So even if one went, at least some of the other functionality would still be there. This would be almost the last thing that I would suspect to have gone wrong.
5.) Critters: Believe it or not, I've had chipmunks chew the wiring in my engine compartment when I left my Jeep parked for several weeks. It seemed almost intentional as they targeted the wires to my starter. Again, the odds of this being your problem - slim. But, if you have what looks like a mouse nest under your seat...
6.) Magical computer stuff: In modern cars, almost everything is controlled by a main computer unit. When you push a button, it sends a code to the computer over a CAN-Bus instead of physically doing something. The computer then controls whatever it is you were trying to do. This is not true for every single thing in a vehicle. And I honestly don't know if it is true for your motorized seats. My Jeep had a feature that allowed 2 separate key fobs to reset things like the seat position, mirror positions, etc. So, depending on who unlocked the vehicle, everything would move back where you want it. This is almost not worth mentioning because, if it is the problem, you probably won't be able to diagnose/fix it yourself unless you are overtly comfortable with electronics. This is also the least likely thing I can think of. I've only had a computer go bad in 1 vehicle in my life. And, when it did, it did not affect just 1 thing. lol