Used to be able to direct challenge my partner, won't work any more. I can still challenge other friends, but when we try it at home one or both computers will search the match for ever or show an "unable to find server" text.
We tried connecting through different wifi networks, or switching devices between pc and cellphones, but won't ever go through.

Important to mention that a few months ago we used to play with no issue at all with the same setting.