Yup. It's unlikely that both transmitters would cease working at the same time, so I agree that it's not the remotes. It's also unlikely they would both lose their coding at the same time, so it's doubtful that "resyncing/reprogramming" them would help.
This points to the receiver as being dead. There's 2 areas in the receiver that would cause this if one of them died: The first is the radio receiver section. If it dies, then the opener will be unresponsive. The second is the actuator section. When the receiver gets a command from the remote, it responds by actuating a relay which is the electronic equvalent of "click[ing] the button on the receiver unit".
Since the button worked, then obviously your motor and drive assembly are fine, so that's one item you don't have to investigate.
There's 2 ways the button could be integrated into the circuit:
1) The button and the relay are wired in parallel so if the relay closes OR the button is pressed, the motor is turned "on".
2) The button is wired into the actuator, so that pressing the button closes the relay which turns the motor "on".
In the first case, the relay could be bad OR the receiver could be bad.
In the second case, the relay would have to be good, so the receiver would be bad.
There are 2 kinds of relays: Mechanical and "solid state". Solid state relays (operating within design specs) are FAR more robust than mechanical relays, but they can still go bad sometimes. Mechanical relays have fairly short lifespans in high-current applications (such as operating high-current motors) and should be the first thing to look at if it's more than a few yrs old.
ADD:
HA!!! Looky what I found! An exploded parts diagram of your remote and receiver:
http://c.searspartsdirect.com/lis_png/PLDM/00032509-00003.png
And here's one for your drive assembly:
http://c.searspartsdirect.com/lis_png/PLDM/00032509-00001.png
In essence, your button is wired into the actuator section as mentioned in #2 above. The actual relay (and although it's a mechanical one, it must be functional or else pressing the button wouln't have worked) is #47 on the above diagram.
So your drive assembly works, your button works, but 2 remotes don't work.
Conclusion: Your receiver isn't working.
BTW, you'll notice arrowed numbers on the above diagrams. If you're interested in the keys to them, here are the key pages:
for the remote and the receiver:
http://www.searspartsdirect.com/par...s/Model-139654021/0247/0718000/00032509/00003
For the chassis assembly:
http://www.searspartsdirect.com/par...s/Model-139654021/0247/0718000/00032509/00001
FWIW, if worse comes to worst, you can swap out the receiver and toss your remotes with a replacement kit for $41.88. Look at #4 on the sidebar of the "remote and receiver" link above. The "converter kit" comes with a new receiver and 2 remotes.
While I'm quite sure that it's your receiver that's at fault, I can't guarantee it without actually putting my grubby little paws on it - if I did, I could tell you EXACTLY what's wrong with it and could probably even fix it for a lot less than $42!
