Why can't I help Sisyphus?

To give some details, I:

• Have given Sisyphus nectar up to his relationship lock.
• Have exhausted his dialogue to the point where I no longer get new lines from him.
• Have completed a full run at least 20+ times since giving him all that nectar.
• Have reliably talked to all the gods in the central hub area between runs.

Despite all this, the option to buy out Sisyphus' contract has never shown up. I've gotten Orpheus' and Achilles' contracts, so it's not just that I'm failing to buy them at all. What could I be doing wrong here? Is there some extra hidden requirement?

After searching around more, I found this Reddit post yesterday:

LPT: If you just cannot seem to get Sisyphus to offer his quest to buy his freedom -- make sure you actually talked to Bouldy.

Once you get far enough in conversation with Sisyphus, he'll suggest you confide your worries in Bouldy. I thought that was just a joke line, but it turns out that once he says that Bouldy actually gains "talk" and "give nectar" prompts of its own that you can access by standing in the right place.

Yesterday I talked to Bouldy during one of my runs, and in the run immediately after that one I had new dialogue from Sisyphus that progressed his personal questline (after making no progress on it for 60+ runs). So I think the Reddit post is correct, and talking to Bouldy as well as Sisyphus is the step I was missing.

The short answer is that the favour will start eventually. Its somewhat unclear what the conditions for certain relationship bits to trigger are, according to Sisyphus' page in the wiki conversations for Sisyphus' favour also lie with Megaera and Hades. With regards to that I recall there being a handful of scenes between Megaera and Sisyphus that occasionally trigger when you visit him which causes Zagreus to become sympathetic towards Sisyphus' plight and eventually decide to free him of his contract. You may have not seen all of those yet and I suspect there's either a certain element of randomness to how quickly these bits occur or you have to visit Sisyphus X number of times which is variable since his room doesn't always appear or you skip it.

For some additional context I'm 120 runs in and I have yet to trigger Hypnos' favour. Besides that I got the quests for those three in a slightly different order, Orpheus first, then Sisyphus and finally Achilles' whose favour didn't trigger until I was 80-90 runs in.