On your host you could try entering the machine manually (from the commandline) and at least then you may be able to see what is going on... (and complete the firstboot scripts and change the logging behaviour as per the link I posted above - although I'm not convinced that is the issue, who knows...).

I am totally unfamiliar with SolusVM so not sure what default settings it would use, I use ProxmoxVE and it all just works OOTB...