and what's wrong when I write that the duo can't do a CI+
But Vu+Solo2 is not a Vu+Duo either
1° the Solo2 is older than the duo
This isn't true. The Duo is older. I don't know the Solo2 but the receiver must be as old as the Duo2, that can handle the CI+. That the Solo2 can read the CI+ must not confirm that the Duo does it either.