Happens to me as well (current chrome w/ vimium on mac), but only after running the example in the emulator.

Before hitting the emulator (and/or editor, not sure) all keys work fine. After, well, only scroll on the mouse worked for moving through the page.

I have similar issue with Chrome 94 on Windows.

It's fine when I initially open the page, but once I click 'run' I can no longer use PgUp, PgDn, F12, etc.

I'm guessing the emulator captures some input. But even when clicking on other parts of the page, it doesn't 'uncapture'.

FWIW, it doesn't really bother me.