Your computer might be missing the required language pack(s).
If you’re having a Windows 8 computer, please download and install the required language pack by going to PC settings → Time and Language → Add a language → Choose the required language → Options → Language options → Download language pack.
If you’re having a Windows 10 computer, please go to PC settings → Time and Language → Add a language → Choose the required language → Options → Language options → Speech → Download.
If you’re having a Mac computer and is running on OS 10.8/10.9, you’ll need to manually add the system voice for the respective languages in “System Preferences – Dictation & Speech” before reading aloud is possible.