it's been a long time since i read the novel but as i remember it was because Diana's no longer serving the people, in the past when she's still a normal person, she genuinely wanted to help those in need (she always pray to God on how she wanted to help, etc etc). But then as the story progress, she's only using her powers to elevate her status, not to mention the Church is corrupt already and it multiplied after she became Saint since she's the living proof of God's existence.
As you can see after becoming the crown princess, she's only healing the king, it might have been a different story if even tho she can feel that her powers are fading, she's still healing the common people.
From what I can gather from other stories and compare is that Diana misused her powers/ stopped using them to help the poor. God granted her divine powers she used it in the beginning to help people, but when she started to get closer to the nobles and stopped helping the temple things started to go downhill for her. Now she is completely crazy in the head thinking she will get it back.
That’s the way I see it in my opinion
Ty man. That helps. I hope it mentions in the manhwa in front if Diana's face
May she suffer even more. I do hope that info get tossed at Diana's face
oh it's worse, until the end she still believe it's not her fault, that it's the other people who caused her downfall
From what I can gather so far since I didn’t read the novel, she seems to want both of them again since she lost her powers. But Heiss is trying to tell her that she doesn’t need her in her life anymore. The way I saw it it’s like saying goodbye. When Heiss said that to Diana she lost it. Almost looked like a threat to me.
But again it’s my opinion
I didn't read the novel and I do remember what everyone else mentioned about Diana not using her powers for the people anymore. But I don't remember there being a panel in the story where they explicitly say "Diana lost her powers because of X". I feel like they have given us some probable reasons like her not being there for the commoners anymore, or perhaps the goddess having lost interest in her (since she got her power from the goddess watching her life). But I don't recall anything being set in stone as the ultimate reason why.
I still wanna know why Diana no longer have her powers. God said she enjoyed Diana and helios story so why remove it? I wish the God explained it bc I'm curious. Is it bc Diana turned to be a bitch or is it that in order to save Kael, she removed her abilities? I would have said that what if hestia , indirectly, wanted it removed to improve Kaelus chances of being alive, but God wrote that down before hestia descended. I just hope it's bc God decided that Diana is such a fucking bitch that even God said bye bye.