Translatepress is a plugin which adds multilanguage support to WordPress with an incredibly easy to use traslation feature directly on your blog frontend.
To make the multilanguage support by Newsletter uniform between different multilanguage plugins (Translatepress, WPML, Polylang and more) this extension adds a language switcher to the admin side when Translatepress is installed enabling the multilanguage configuration sets of Newsletter.
It adds of course the language support during subscription, cancellation, profile editing and the language-list linking feature of Newsletter to have a full translated user experience while interacting with Newsletter.
Please refere to the Newsletter multilanguage documentation page for details on how correctly use the multilanguage support.
The language slug and 404 errors
If you experience wrong URL or 404 errors when visiting the newsletter public page, the profile page or the unsubscription pages, it could be the language slug of your default language is in the format xx_yy.
Try to set it to the forma xx (for example en and not en_gb), we saw it helps. Anyway we was not able to reproduce systematically the problem.
Posts block and per language content (not working)
Due to the nature of Translatepress, there is no support for translated post extration while composing a newsletter or on Automated extension.