Hi,
Since i had the EXACT same problem after switching to another internet service provider, I thought I would share my solution.
My VPN would connect, but when it did I couldn't access any sites anymore, they would just keep loading forever. The sites would immediately load when I switched Secureline off.
The thing that did it for me, was to change the MTU value of the Secureline connection:
Go to the Network and Sharing Centre of Windows > Click Secureline > Properties > Configure > Go to "Advanced" > Click on MTU (standard value was 1500 for me) > Change value to 700. Click OK. Secureline should be restarting and reconnecting.
For the record, my internet connection started working again from a value of 1300.
I hope this solution also works for you and other people encountering the same problem.