Did you need to cut off the magnetic switch from the SPS20 to install a universal connector ? If so and you had a battery connected to the SPS20 when you cut the wire you probably destroyed the SPS20. I wasn't paying attention and forgot to disconnect the battery and wrecked a DSM10 this way.
If you reconnect the magnetic switch to the SPS20 can you power the receiver on/off ? If so, then the SPS20 is fine, disconnect the magnetic switch and connect the the R3/RSW, port 3 in it's place. Make sure you get the polarity correct. It shouldn't hurt anything if you get it backwards but it won't work either.
If that is all connected correctly and it still doesn't work then there is something wrong with your R3 setup or the R3 itself. When you go into the device explored and select the RCSwitch menu does it show up properly while it's connected to the SPS20 ? If not, it probably isn't receiving power from the SPS20.
Once you get it working, the R3/RSW draws quite a bit of standby current (about 25mah) so you MUST disconnect the battery from the SPS20 between flying sessions.