It was working before with no issue, but now for some reason it doesn't allow me to grab the issue that is part of the epic to the first iteration of my Program Increment. It works if I move the epics to another iteration. That epics belong to a Kanban board (ARQ), and the iteration/sprint dates are determined by other boards that are scrum. I have this issue for this team, and for the first iteration only. This is what I have done so far with no success:
- Remove the epic and create a new one with the same name
- Remove the issues and create new ones with the same name
- Remove the program increment and create a new one with the same configuration
- Remove the program itself and create a new similar one
- Remove the sprints from the scrum boards and create a new one with a similar name
- Move another epic from ARQ board to first iteration and try to plan it, same situation it doesn't allow it
Here is the picture:

The gray background seems to mean, something is broken or that iteration cannot be planned for that team. If I unselect this epic, it shows the entire column with the same color:

Have you seen that before, I don't know what else to do. Thanks for any help.