This is a pretty dense review, but it covers your topic extensively. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4544655/

To briefly state one point they examine; the changes in glycogen levels observed in the sleep/wake transition, may be more diagnostic of that transition happening, and not actually a causative agent of that transition.

Similarly two other reviews examining the role of adenosine in sleep found that while adenosine does have a role in sleep, it is much more specific in its function, not a master "go to sleep" signal https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2769007/, and that the role adenosine takes changes depending on where in the brain, and what receptors it is working on https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6650574/

Looking around for publications, its clear that there is a lot of work being done and different camps with different models they are testing. I don't think their is a complete mechanism that everyone agrees on.