Johan,
So the reason that section is greyed out is that Polylang isn’t recognizing the content blocks as custom post types. I tried installing a different content block plugin (Reusable Content & Text Blocks by Loomisoft) and the section is active, and allows me to enable Polylang.
https://i.imgur.com/Xp1FzFD.jpg
Polylang is a great alternative to WPML because its free version is suitable for most applications. WPML free is limited to 2000 words, which is very restrictive.
Thanks, Josh