Perhaps is a problem similar to this one where the configuration is not supported. Try and look at the fifo.log.
- From a Guacamole connection to a Firecracker VM (fails):
The VNC server which firecracker uses is different from KVM. The output of a screen session is exported on a port in the host. If the VM is not running this will not work. In any case, you can look for the processes screen and svncterm on the hypervisor node.