Problem
When adding a specific language, zero translations are imported for that language even if imports are enabled. Not all languages are affected.
Steps to reproduce
I seem to be able to enable a language, delete the language, and then enable the same language again. This results in zero translations imported.
Cause of issue
Even if a language has been deleted, locale does not clear it's cache entry in it's locale.translation_status key_value collection. It seems that the presence of this cache entry lingering causes a future import during a language add operation to result in zero imports.
Steps to address
When adding a new language, clear that language's translation cache entry in the locale.translation_status key/value collection in locale's add language submission handler.