I work from home most days, and my work still uses a PPTP based VPN. While that's insecure and has been blocked in iOS 10, it's not something that I have control over. I was happily able to connect to the VPN yesterday but from this morning onwards my connections are being blocked somewhere between my laptop and work.

I'm using Windows 10, and the error message that I'm getting is:

"The VPN connection between your computer and the VPN server could not be completed. The most common cause for this failure is that at least one Internet device (for example, a firewall or a router) between your computer and the VPN server is not configured to allow Generic Routing Encapsulation (GRE) protocol packets. If the problem persists, contact your network administrator or Internet Service Provider".

I know that the VPN is working as I have been able to connect to it from an AWS server, and I have colleagues who have connected as well. I've ruled out it being an account issue as I was able to use the same account on the AWS server. Nothing has changed at my end that I know of, unless there has been an automatic update on my router (Huawei B315s).

That leaves the Spark network as the only unknown in the equation. The person I spoke to at the Spark helpdesk didn't even know what VPN was, let alone PPTP or GRE so I didn't really get anywhere there.

I read in other forum topics that changing the APN settings can help, but the APNs listed here (https://www.spark.co.nz/help/mobile-data/troubleshooting/spark-apns-and-ip-ranges/) don't seem to work for Rural Wireless Broadband.