@jbgerber I had the same problem….
All feautures of Polylang Pro worked like a charm except String Translation for Woo.
The reason was that the Default site Language (before Polylang installation) was… Lets say No1. After Polylang installation, i set as A default Language No2 (via Polylang)….
in this way woocomerce strings never translated! So i turned the default language back to No1 and this Fixed the issue… Hope it helps you cause, i also tried everything ??
PS: with different theme in my case!