Did u put the update of Mariokart that is on the HShop? I had the same problems but since i updated it it works normally, try it

oh nvm i put the answer for a 3DS, but still, try it

This happened to me too but the more i used Pretendo the disconections became more rare. So I guess just keep using it and see what happens and if you still have problems there most definitely is some Reddit thread explaing how to solve the issue. :)

thanksfor all the answers