Package: x2goserver
Version: 4.0.1.20-1.el7.x86_64

Package: x2goplugin-provider
Version: 4.1.0.0-1.el7.x86_64

Package: x2goplugin
Version: 4.1.0.0-1.el7.x86_64

All packages are from the official EPEL 7 repository.

When trying to log in using the firefox plugin, the error is:  Failed to
connect: Permission denied.  The same credentials work with the x2go client.

I used the example X2Go Demo config file, only changing server=IPaddress.