There appears to be a bug in WordPress 6.1 which prevents the plugin translations from loading when displaying the confirmation message to a user in a language other than the current page language.
To reproduce, follow the test steps in the SwitchToEnglishCest acceptance test (which is failing on 6.1 because of this) and observe the message is output in the current page language instead of the language of the user you just switched from.
There appears to be a bug in WordPress 6.1 which prevents the plugin translations from loading when displaying the confirmation message to a user in a language other than the current page language.
To reproduce, follow the test steps in the
SwitchToEnglishCest
acceptance test (which is failing on 6.1 because of this) and observe the message is output in the current page language instead of the language of the user you just switched from.git bisect
tells me that 54682 is to blame.https://core.trac.wordpress.org/ticket/57116