While a lot of quests there require only level 10, I see a lot of Campaign quests (with the brown shield around it) icons indicating that they require level 60.
This does not shock me. (Actually, nothing about Shadowlands shocks me - it was, and remains, a mess.) Some post-cap campaign quests do require a character to have achieved the equivalent cap of the expansion.
If that’s the problem, I am a bit surprised, though, that your quest log doesn’t say something like “Reach Level 60 to continue the campaign.”
This support article lists some vague possibilities
It does say
In addition, chapter 8 Envy and chapter 9 Dominion require that you first unlock the Mirror Network and complete Laurent’s storyline Mirror Maker of the Master which starts with the quest An Unfortunate Situation in the Ember Ward.
but if you have completed Ch 8, can that be blocking you from Ch 9?
This guide lists what it says are the necessary Renown levels for the chapters: