Update github.md

github.md

@@ -12,3 +12,18 @@ Be sure to activate the plugin. When it's done, you'll see a link in the log in
 
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+## Debugging
+
+If you can't log in with your GitHub settings, please check the logs of `xo-server` while you attempt to connect. It will give you hints about the error encountered. You can do that with a `tail -f /var/log/syslog -n 100` on your XOA.
+
+## Missing plugin?
+
+If you don't find the GitHub plugin in the list, be sure to have it displayed in your Xen Orchestra configuration (in `/etc/xo-server/config.yaml`):
+
+```
+plugins:
+
+  auth-github:
+```
+
+If it's not the case, don't forget to restart the service after your modification, with `systemctl restart xo-server.service`.