On App Store Connect, in Localizable Information of App Information of my APP, the drop down list of languages shows English(U.S.) only, I can't choose and add other languages to localize app name or app description. Does anybody know the reason? Thanks.
Not sure if this helps, my project is using Xamarin Forms, and I already added [language].lproj folder and InfoPlish.strings file. I could search my app's English name on App Store, after installed, it'll show other language's app name if changed my iphone to that language.
In that same dropdown menu, you are able to select a new localization for your app but this is only possible when you are doing a new submission (your submission is in Edit mode).
The image below shows the different localization options I have available for an app that is ready to be submitted for review.
Hope this helps.-