Here is the contents of the log:Please post the full logfile (HOWTO is in a sticky thread in "General Support")
All specified ports are open. With disabled Firewall, the same error.It looks like network problems when the server tries to legitimize itself with steam. Here is some information about ports needed:
https://community.7daystodie.com/topic/3998-support-faq-information-and-common-solutions/?do=findComment&comment=47970