Lighthouse scores unavailable for minimal mistakes sites

[anupamck]

Once I built my website with minimal mistakes, I tried to evaluate its Lighthouse scores. I kept ending up with an error:

LighthouseErrorSummary.pdf

No metrics are available because of the following error:

The page did not paint any content. Please ensure you keep the browser window in the foreground during the load and try again. (NO_FCP)

This is true of all minimal mistakes sites I have tried so far - even the landing page for the theme itself. Any idea why this is happening, and how to get around it?