To clarify:
On my home network, I use Cloudflare's custom DNS Resolver (its a setting I put in my router) a lot like Google's custom DNS, and it blocks a lot of shady websites from loading. I suspect Starbucks uses the same or similar.
I checked your website while _not_ connected to my homenetwork nor SBUX, using my phone's 5G internet (which probably uses a Google DNS Resolver), and your site loaded fine.
Thus, your domain appears caught in at least Cloudflare's block list.