Advice with my duo

Me and my mate, we have played for years, of course some times we play alone, in fact most times alone, but every now and then we will have a duo weekebd, and surprisingly, we always get demoted.

Now, I win alot by myself, same as my friend, but it's not as fun

So I choose to duo with my friend, but everytime, we lose,

It's impossoble for us to win,

Just wondering, has anybody else come across this before?