I like the beginning of the logline that tells us what has happened, he has failed his final mission to receive wings and graduate to guardainship, but I agree with the other comments that it is a bit confusing who the Main Character is.
If the MC is the angel I want an adjectiv that tells me something about the MC's flaws, like you did with the "depressed mime", that is a good character description, and it's maybe because you describe the mime and not the angel it feels uncertain who your MC is. And if the MC is the angel,why is it imortant who this client is?
I would like to know something more about the story, what will happen? How will he help him discover reasons to continue living? I can't really picture what they might be doing reading the logline as it is now.
And more importantly, what will happen to the angel if he should fail? What is his stakes? He has already failed his final mission to receive his wings, so something worse than that has to happen and it need to be in the logline.
Also, how is this helping him to receive his wings and graduate to guardianship, have someone told him that if he does this he will win his wings? You should think about putting that in the logline aswell.
Something like this maybe?
When an arrogant angel fail his final mission to recive his wings and graduate to guardianship, his only hope for a second chance is to show a depressed mime that life is worth living, or he will be kicked out of heaven.
Good luck!