This behavior is possible if files that relate to SolidNetWork Licensing (SNL) are missing. For examples, “sw-d.exe”. This can happen when an unknown program, such as an anti-virus program. They removed the ‘sw-d.exe’, ‘lmgrd.exe’, or other files.
In order to resolve the issue, SolidWorks need to be repaired. Please go to the wiki-link How to repair SOLIDWORKS, there is the steps to repair SolidWorks.