Turns out the language setting in the info.plist was wrong. It was set to Spanish, but should have been es (so the app defaulted to English).
<key>CFBundleLocalizations</key>
<array>
<string>en</string>
<string>es</string>
</array>
In property list view it shows en as English so I assumed I should use Spanish. Only noticed the difference when I viewed it in source code mode.