You should have given both PCs "fixed" IP addresses and not enabled Internet Connection sharing on either of the Dialup connections. Have you set it up this way?
Try using fixed IP addresses of 10.0.0.1 and 10.0.0.2
Huawei P10 review
1995-2015: How technology has changed the world in 20 years
An overview: What leading creative agencies are doing to improve diversity
New iPad, iPhone SE & Red iPhone 7 on sale now
Synology invites you to visit them at Insomnia on 26th – 29th August. Book your tickets now and visit Synology.