Apple disabled native PPTP VPN in macOS Sierra for good reason – it is highly insecure. However, sometimes for reasons completely outside of your control you need to use a PPTP VPN. Luckily, there is a free option through Flow VPN:
https://www.flowvpn.com/download-mac/
Once you download the client, simply type in the VPN address such as “pptpvpn.dal01.softlayer.com” with your username and password. PS – You can find a full list of SoftLayer PPTP VPN urls at the bottom of this guide: https://knowledgelayer.softlayer.com/procedure/set-pptp-vpn-mac-os-x-10x
I did observe a defect while working with SoftLayer and Flow VPN. Your password cannot have the “#” special character in it or you will get invalid password errors. I couldn’t tell if the defect is with Flow VPN or SoftLayer.