Never. I've never had it work at a Marriott property, despite having no trouble using mobile keys with Hilton before 2018. I currently use a US-market LG G8 with no mods or unlocks/roots. I haven't even had the moblie key logo show up in the app where it is supposed to according to the Marriott documentation, even when standing at the front desk and having them manually "reset" it. Upon check-in the app always says I have a mobile key and can go straight to my room, but it's never worked, not once in dozens of attemps. I've uninstalled/reinstalled the app, cleared data and cache, etc, no luck.