As far as I can tell.. the rack doesn't come with the AC to DC adapter/transformer.
https://www.sweetwater.com/store/detail/HappyEndBK--tiptop-audio-happy-ending-kit-black
Power supply
https://www.sweetwater.com/store/detail/ZeusBoost--tiptop-audio-uzeus-boost-mantis-universal-adapter
I could be wrong. I'd check with whatever seller you buy it new from.
Though, the used prices are nice and come with a wall-wart as far as I can tell.
s://www.ebay.com/itm/Tiptop-Audio-Happy-Ending-Kit-Black-Eurorack-Modular-Kit-with-Power/153752311346?hash=item23cc5a1632hfQAAOSwubdd6oOF" target="_blank">https://www.ebay.com/itm/Tiptop-Audio-Happy-Ending-Kit-Black-Eurorack-Modular-Kit-with-Power/153752311346?hash=item23cc5a1632hfQAAOSwubdd6oOF