Among these 3 free PPTP VPN services, Free VPN Servers is not available any more.
But luckily, there are and will be always some other alternatives, such as the following 2:
1. Zace Book
At the end of the Zace Book Free VPN page, you can see a free PPTP VPN account, such as the following:
By the way, there is no link to the above page indeed, and if the Zace Book site is blocked in your area (such as China), you can try to replace "vpn.zacebook.com" with "18.104.22.168".
Besides free VPN, Zace Book also offers a free online proxy, but which is blocked in China, too.
2. VPN Book
On the Free VPN page of the VPN Book site, you can see the PPTP VPN service account directly, such as the following:
Besides "euro1.vpnbook.com", you can also use "22.214.171.124" as the server address.
Whether Zace Book or VPN Book, their passwords will be automatically changed every 24-48 hours, in fact, they are developed by the same guys I think, since their servers are both hosted at Voxility S.R.L. with Romania IP addresses, and what is more, there is a link to VPN Book on the Zace Book website.