Wii U EU, Splatoon 2.12.1 Code 118-0502

[modern tapir]

Wii U EU, Splatoon 2.12.1 (disc), Aroma + Inkay 3.0.0. Juxtaposition works, Pretendo login works, but I can't join public or private lobbies. Matchmaking searches for players and then fails with error 118-0502. I tested a new Pretendo account, a new Wii U user, home Wi-Fi and a mobile hotspot. My friend can play at the same time without issues.

[tropic gyro]

118-0502 (Wii U)

Support code detected, press to expand information

[viral marsh]

It's usually not common for two different connections to result in this error, so it may be an issue on your friend's end, just to confirm it may not be an issue on your end, could you please perform a connection test in your Wii U's System Settings and provide the support code displayed in the bottom-right corner of the Gamepad screen?

[modern tapir]

I performed the connection test successfully.
Support Code: 220-00.
The connection test completed successfully.

[viral marsh]

You have NAT type C, it may be an issue on your end
Just to double-check, do you recall the support code that you got when you set up your Wii U to use your mobile hotspot? Assuming you didn't skip that part of setting up a Wi-Fi connection

[modern tapir]

I don't remember the support code from my mobile hotspot connection. I don't think I ran a connection test with it. I can test it again and let you know.

[viral marsh]

Do that please, it may be that your mobile hotspot was also NAT type C or worse

[modern tapir]

I tested again using my mobile hotspot the connection test was succesfull Support code 220-01

[viral marsh]

That's NAT type D
For your home Wi-Fi, you can try using the pointers in the NAT Check Guide to try and improve your NAT type, however past that we cannot provide specific instructions since routers may have different configuration pages and capabilities
I'd recommend doing your own research into how to improve your NAT type up to either B or A and/or contact your ISP to ask them on getting a better NAT type