Glad to share my findings! I was bummed for about a week when I thought the Web App was gone for good (it’s the only place you can add/modify sensors) but then I randomly figured out a slightly different URL to access the app and was happy to find everything working.
I really like this product (Hook) too! Since purchasing my Hook just over a year or so ago, I ended up buying a Broadlink RM Pro, mainly because I really needed to be able to work with both 433 and 315MHz RF devices. At first the RM Pro was a total pain to work with - the provided app was absolute garbage, but now the app works decently enough and there are a number of workarounds. The device also works with IR signals as well, which is useful. However, there are no other devices out there that I’ve been able to find (aside from Hook) that allow you to use the device as an IR receiver as well, aka, the “Sensors Beta” feature. It’s really great being able to inexpensively add additional wall switches and remotes, doorbells, etc. to my home. That’s the one main feature I’ll be most upset to lose if the Hook crew does eventually decide to pull the plug. But I agree - Hook is simple to work with, and has been very dependable and solid.