SolidWorks uses FlexLM for the network server. If you can't access the server, go to Start > Run > services.msc and locate FlexLM in the list. Right click it then choose Restart. This will restart the service. Secondly, access the FlexLM interface and make sure that everything is working normally. If the settings are configured correctly and the FlexLM server is working, SolidWorks should start normally.