On Xbox One.
1) In Director, select Crucible, then click on Iron Banner Icon to start a match.
2) Wait until it starts adding people to the match (i.e like 4 / 12, or 6 / 12 etc.).
3) Being tired of waiting, I click the "Cancel" button and go back to Step 1.
4) The Iron Banner Icon will not Select and will NOT start the match. No Error code, just a message to the affect "This Activity is not Available".
5) Repeat step 1 for the next 1 to 5 minute or so until the game grudgingly decides to let me back in.
This is not 100% repeatable but it has happened 10 times this week during Iron Bladder with my 3 different characters.