You may not be able to open your cPanel if your local connection has been limited / filtered. In such cases you should try accessing your cPanel through:
1) if you are a SiteGround customer, you can log in from your SiteGround Customer's area, My account and click on "Go" under cPanel's column for your account.
You will find two possible ways to access the cPanel - via secure or normal connection. In case your ISP filters the connection and blocks the standard secure cPanel port (2082 or 2083 ), you will have to use the normal connection.
2) Alternatively, no matter whether you are a SiteGround customer or not, you can access your cPanel directly through:
http://www.yourdomain.com:2083 (for secure connection)
http://www.yourdomain.com:2082 (for normal connection)
SiteGround offers the best cPanel hosting package. With it you can access and manage your cPanel without any problems.