What could be the reason of showing the licence inavlid?
There is various reason why your license showing invalid. Follow the some easy steps to check why its showing inavlid.
Reason 1). login in you WGS Client area and then check your services activated / Terminated or suspended. If you are getting status like suspended or terminated that means you haven't pay the invoice.
Reason 2). Check the license path and compare with whmcs base dir path. To check the path login in your WGS client area and on dashboard you can see the active product and here you can find the Manage Service link click on that icon it will redirect you on Product Service details page under domain section you can see the Installed license path if your path is invalid than it will show you invalid license so just reissue the license or open the ticket to WGS support team here
Reason 3). Another reason could be your firewall blocking the license check request . To check the WGS site communicating with your server or not , Open the terminal and login in your server and run the curl https://members.whmcsglobalservices.com or telnet https://members.whmcsglobalservices.com if you are not getting the response that means your server is not communicating with WGS site. To fix that allow the WGS site domain in your firewall.