I've read through this a few times. I've tried deleting the plugin and the trakt.xml file a few times and I can't seem to get authenticated.
I've got a fresh install on Fedora 27 that I've been trying to get setup.
Server logs are attached but they didn't tell me much.
Have you tried to revoke the access over at Trakt? You can do that through your settings somewhere, look for a tab called "connected apps" or something similar, delete the Emby token and try again.
Trevor68 had to do this and I did it long before I got it to work so I'm unsure of the impact. But it's worth a try.