The device's primarily-marketed feature is opening your garage from an app. To do this, the app and the device talk through the company's server. This developer blocked the customer's app from the server. That breaks the device's primary functionality.

As a side note, I wonder about the original app design, I mean, Wi-Fi/Internet connection is down and I cannot enter my garage (unless I still have anyway handy the original garage remote or key), the company's server is down (for whtever reason) and I am locked outside the garage, there is a DDOS on (say) Cloudflare and I am locked out of the garage ... :(

Usually this kind of hiccups happen not in a sunny warm day, but when it is heavily raining, during a storm, etc.

This is a major flaw with a lot of technology now. The assumption that you will have an internet connection. It's horribly inefficient, especially when we have robust p2p wireless protocols.

Since Garadget deliberately and maliciously disabled the device, can the consumer sue for compensation for the time wasted on it?

Yeah, I misinterpreted "device" (as "iPhone").

The device is useless without the app. They disabled the device.