Mine's selected as max lair(I checked it) and the dynamax level is indeed 8(I did not change anything other than rerolling it to a Xor=1 shiny). I tried it with a Zygarde(a Xor=1 shiny) and it still shows this error and yes, this one is also dynamax level 8. I made sure it's selected as max lair(as seen in the photo) but this message keeps popping up even if I clicked on the green tick legal check button.