Are you using free version of Polylang?
Well, with its latest version you’re not able to translate widgets when you use new Gutenberg blocks environment.
With this plugin you can set visibility based on current language for any block, not only in widgets.
If you’re use FSE theme, then you’re probably missing some Language switcher block, right?
Well, this plugin will fix also this problem for you!
Language switcher block with all needed settings.