Misc [Help] Error code 001-0502 on both 3DS and Wii U

[Ryuzaki_MrL]

This occurs everytime I try to play online or access the friend list, and it's happening for 2 months now.
Stuff such as eShop, Miiverse, and everything else besides online play (specifically when involving the friend list feature) is working just fine. (Pokémon shuffle's check-in and Pokémon XYORAS' Mystery Gift works, but not the PSS).

Nintendo's Costumer Service website states that I need to forward some ports within my router's settings. I've already tried that with no avail.

Also tried setting up a DMZ host for both my 3DS and Wii U, resetting my router's settings, resetting both my 3DS and Wii U's internet settings, disabling my router's firewall, and enabling port triggering. Still won't work.

It's also worth noting that this same issue also occurred when testing on my neighbor's wifi, who has the exact same router as mine (they are provided by the local ISP).

 

[Stellar]

I have this exact problem, and I didn't have it before. Nothing fixes it.

 

[Stellar]

For what it's worth, I found a fix for my issue: get a new IP. In my case, simply rebooting the router wasn't enough. I had to leave it unplugged overnight for my ISP to assign me a new one.