Matchmaking error in hardly every game or app between 3ds

[runic falcon]

I have a problem when I try to matchmaking with friends in smash Bros. Mario kart and friends app in pretendo. Every time we try to play together in a private rooms with friends, they give an error like 018-0510, our Nan type is type B, apparently the errors occurs when we try to play together, Including public rooms, we tried to solved it enabling and disabling pretendo, but it didn't work, we checked hardly everything possible, but we don't know what to do

[balmy ferry]

018-0510 (3DS/2DS)

Support code detected, press to expand information

[fervent mauve]

did you checked your friend's nat type?

[runic falcon]

To add, I deleted my friend and now I can't add him again, I don't know why, the just keep in wait a moment

Yes

Both are type B

Another error, in monster hunter

@fervent mauve my Nat is type B, and my friend's nat is type B too

[fervent mauve]

try again for that

[runic falcon]

Ok

It worked

Did you changed something?

[fervent mauve]

nah, that one happens sometimes

[runic falcon]

Ok, I understand

But what happens with friends list and smash? What can I do?

There is any solution?