TypeError: (void 0) when trying to run example.

I've been trying to evaluate workers for an upcoming project, and I'm struggling. I used this example, replaced all the config variables, yet can't seem to get around the following error. Can't quite figure out how to get "prettified" JS to work in preview console, or to build it with non-minified. Was hoping the example would work out of the box, but wrangler generate, add the secrets (confirmed they are correct and available) leads to this error.

Uncaught (in promise)
TypeError: (void 0) is not a function
at worker.js:76:207404
at Array.reduce ()
at a (worker.js:76:207352)
at Object.resolve (worker.js:76:209116)
at t.resolveMiddleware (worker.js:76:251451)
at t.e.send (worker.js:76:209572)
at worker.js:31:35587
at worker.js:31:35653
at worker.js:31:35759
Uncaught (in response)
TypeError: (void 0) is not a function