Please try updating your voicebank to the latest version. Theoretically, all AI voicebanks support cross-language function, and only the latest version of the voicebank can support it.
「いいね！」 1
The update wasn’t available last night, but finally this morning it let me download it and Seika now has all cross-lingual options 
I guess, like I said earlier, they were just waiting until it was the 27th in the US to make her fully usable
「いいね！」 3