I am having the same issue. Doing a network firewall trace, when I try to connect to another PS4 over the internet, I see the connection from my private RFC1918 IP going to their public IP via my public IP. However all of the sudden my PS4 tries to connect directly to their RFC1918 IP address, which will never happen, as a 10.x.x.x isn't allowed to talk to a 192.168.x.x over the Internet. This would explain why the connections work on the same wifi/lan, but not over the Internet.
Both playstations are set to NAT Type 2, and all other games work that require PS->PS communications, it is just Minecraft that won't connect.
Jason Grove
I am having the same issue. Doing a network firewall trace, when I try to connect to another PS4 over the internet, I see the connection from my private RFC1918 IP going to their public IP via my public IP. However all of the sudden my PS4 tries to connect directly to their RFC1918 IP address, which will never happen, as a 10.x.x.x isn't allowed to talk to a 192.168.x.x over the Internet. This would explain why the connections work on the same wifi/lan, but not over the Internet.
Both playstations are set to NAT Type 2, and all other games work that require PS->PS communications, it is just Minecraft that won't connect.