E202 - font_scale must be > 0

Cause

A slide's font_scale: is zero or negative. The scale is a multiplier applied to the base font size, so non-positive values would collapse or invert text.

Example

{ title: "T", elements: [...], font_scale: 0 }

How to fix

Use a positive multiplier. The default is 1.0; common picks are 0.75 (smaller) or 1.25 (larger).