Progression of Support Ranks
As you may have already noticed, you have enlightened Support ranks in the list, but it is impossible to trigger discussion between the characters. There are several scenarios:
When it comes to Byleth, the conversation proposal will arrive one day in the week when the conversation proposal will only be available on the monastery map in free time mode.
In almost all cases, it will be necessary to wait until sufficient progress has been made in history to develop Support beyond a certain point. This may be after a certain chapter at the academy, or after the 5 years, or even after a certain chapter in the second part of the game. Many relationships are blocked after rank C, or even B, and they can only reach A in the second part of the game.
You can accumulate as many potential S ranks as you want on Byleth, but you can only choose one, near the very end of the game, just before the final battle. This will be an opportunity you can't miss, no need to worry.
There are some cases where you only have a limited amount of time to develop Support between characters. If you do not develop their relationship quickly enough, the opportunity will be missed forever. Fortunately, this is still rare. The most notable example is Rhea, you must develop the first two rows before the dance competition, and the third before chapter 12. But it is also valid with some of your students, especially house leaders, it is better to activate ranks C and B as soon as possible to be sure not to miss an opportunity to strengthen your relationship.
Written by Robin "Raiden" Bouquet. Translated from French by Millenium.us.org