Hello and thank you,
No, I didn’t import from other plugins. I proceeded as I have done every time from my last 15 sites: I just installed Squirrly.
Everything seems OK in automation.
The snippet in the pages/posts has disappeared since my last 3 WP sites.
I can access snippets from elsewhere, such as from page or post lists, but not in their individual views.
In the latter, the seo snippet zone appears, but remains empty, whether it is open or closed.
I suppose a problem following a WP update or plugins update (all sites have ACF and classic editor in common).
[ Translator link deleted ]