**Steps to replicate the issue** (include links if applicable):
* in multi-language wiki (wikidata,meta,mediawiki) . I will use wikidata urls as s example
* you have set a global interface language in [[https://www.wikidata.org/wiki/Special:GlobalPreferences#mw-prefsection-personal| (Internationalization section) ]] no matter what language you choose in global preferences (for example Spanish)
* you set an exception for interface language in the wiki [[https://www.wikidata.org/wiki/Special:Preferences#mw-prefsection-personal|(Internationalization section)]] by checkbox of ``Set a local exception for this global preference.`` and set the language to English in same page.
* go to any other page [[https://www.wikidata.org/wiki/Wikidata:Main_Page|main page for example]].
* open top language selector and try to choose any other language (Deutsch for example).
**What happens?**:
the interface language remain English
**What should have happened instead?**:
the interface language must changed to selected language
**Remark**: I can change the interface language from preferences.
this bug checked in chrome and firefox. wikidata, meta and mediawiki got same result.
== Developer Notes ==
The `globalpreferenceoverrides` API is not working although the response was `{"globalpreferenceoverrides":"success"}`
Likely to be caused by recent works on T323076.
The ULS may also consider switching to a simple `new mw.Api().saveOption( 'language', langCode, { global: 'override' } )` call facilitated by T323076.