It works very intermittently for me (Chrome on Windows, with plenty of RAM and CPU).

When I click the "speak" button, it makes a network request (as shown in the Chrome devtools) and immediately gets back a response that looks big enough to be an audio blob.

But most of the time, instead of actually playing the audio, it just sits there with a spinner for anywhere between 30 seconds and 5 minutes before giving up, with no errors in the console.

Works for me. Whats your machine like?

Sadly it is like this:

OSX 10.13

Model Name: Mac mini Model Identifier: Macmini7,1 Processor Name: Intel Core i5 Processor Speed: 2.6 GHz Number of Processors: 1 Total Number of Cores: 2 L2 Cache (per Core): 256 KB L3 Cache: 3 MB Memory: 16 GB