Dynamic queue party error

So I was banned last season for being toxic, and as a consequence I did not receive a border or ranked rewards. I ended last season platinum 5, and I found I could not duo with another friend who ended plat 5 as well due to our need to "be one tier within each other". Is this an error, or simply a further consequence? Would be great if a Rioter could respond.

Thank you, LightNoch