is your wireless connection unstable and unreliable?
specifically,
when i am trying to find some matches on Metroid
it searches, finds a person or two, then just drops them and starts the search all over again
i even bought the piece of shit wifi usb connector to strengthen the signal of my DS but that thing is a piece of buggy shit.
It does take a while sometimes, but I think it does work fine once it does connect. I do get that thing where they come up then disappear, but I think its just looking for an optimal connection.
Is your regular internet unreliable? I’ve had zero problems with DS wifi… so maybe it’s your connection. Like stated earlier, it can take quite a while sometimes however.