I disconnected everything and reset to factory default. Then I connected PLM and Switchlink and crosslinked them. Then I connected to LMCE core and recreated the PLM device. I checked the PLM log to see if it found the hex address of the Switchlink - it did.
I used admin to manually add a light switch device. When I reset the router and returned to admin to look at the device, I saw that the configuration box had been magically filled in (no longer just asterisks). The light did not work at first, so I thought I still had problems. But after a few minutes, I had a working switch. I wish I could say that I identified and solved the problem I was having - maybe the insteon devices were not properly crosslinked.