Unable to Connect to Multiplayer Game

Hi everyone,

I'm encountering issues when trying to connect to a multiplayer game with a friend of mine. When I try to join his game I'm always stuck with trying to connect. If he wants to join my game it says connection failed.
We are also unable to connect to a LAN game via Hamachi. Anyone got some hints what we could do?

We both have UPnP enabled and I can see that Port mapping is created when I host a game...

Log:
[INFO][app]: SpellForce2 Final v2.68.5408
[INFO][app]: OS version information: 6.2.9200 Service Pack 0
[INFO][app]: Physical memory total: 16323 MB
[INFO][app]: Physical memory available: 10069 MB
[INFO][app]: Virtual memory total: 4095 MB
[INFO][app]: Virtual memory available: 3917 MB
[INFO][app]: PageFile memory total: 18755 MB
[INFO][app]: PageFile memory available: 11400 MB
[INFO][app]: Memory load: 38 percent
[INFO][app]: Number of processors: 4
[INFO][app]: CPU GenuineIntel family 6 detected.
[INFO][app]: CPU clock speed is ~3312 MHz.
[INFO][Create Device]: Switch to display parameters: 1920 × 1080 @ 60 Hz, fullscreen.
[INFO][Create Device]: Vendor ID = 0x10de
[INFO][Create Device]: Device ID = 0x1b81
[INFO][Create Device]: Subsystem ID = 0x33021462
[INFO][Create Device]: Device name = \\.\DISPLAY1
[INFO][Create Device]: Device description = NVIDIA GeForce GTX 1070
[INFO][Create Device]: Driver version = 21.21.13.6930
[INFO][Create Device]: Driver description = nvd3dum.dll
[INFO][Create Device]: Vertex shader = 0x300; Pixel shader = 0x300.
[INFO][Create Device]: Testing sRGB support for display format 0x15, pass.
[INFO][Create Device]: Testing sRGB support for display format 0x16, pass.
[INFO][Create Device]: Testing sRGB support for display format 0x15, pass.
[INFO][Create Device]: Testing sRGB support for display format 0x16, pass.
[INFO][Create Device]: Testing sRGB support for display format 0x31545844, pass.
[INFO][Create Device]: Testing sRGB support for display format 0x33545844, pass.
[INFO][Create Device]: Testing sRGB support for display format 0x35545844, pass.
[INFO][Create Device]: Engine color space is linear.
[INFO][Steam]: Received stats and achievements from Steam
[INFO][NET]: UPnP: default gateway is 10.0.0.138
[INFO][NET]: UPnP initialization failed while creating static port mapping collection, hr = 0
[INFO][NET]: UPnP: failed to add port mapping from port 2802 (UDP) to 10.0.0.2
[INFO][NET]: Local-Host-Address #1 (NAT resolved): 2620:9b::1952:ac35:2802
[INFO][NET]: Local-Host-Address #2 (NAT resolved): fe80::117d:81d7:fd1:780f:2802
[INFO][NET]: Local-Host-Address #3 (NAT resolved): fe80::5c04:25b5:1765:179e:2802
[INFO][NET]: UPnP: default gateway is 10.0.0.138
[INFO][NET]: UPnP initialization failed while creating static port mapping collection, hr = 0
[INFO][NET]: Trying to connect to 46.5.2.84, Port 2802
[INFO][NET]: Connection failed, result 0x80158510
[INFO][NET]: Trying to connect to 127.0.0.1, Port 2802
[INFO][NET]: Connection failed, result 0x80158510
[INFO][NET]: Trying to connect to 192.168.0.59, Port 2802
[INFO][NET]: UPnP: default gateway is 10.0.0.138
[INFO][NET]: UPnP initialization failed while creating static port mapping collection, hr = 0
[INFO][NET]: Trying to connect to 46.5.2.84, Port 2802
[INFO][NET]: Connection failed, result 0x80158510