> What's the issue here?

You need to know previously the word to write from Hepburn to Kana when "ō" is present because data is lost in such transliteration from おう or おお or オー to Hepburn.

The internet is full of romanji written incorrectly with "o" alone when it should be "ou" or "oo" due "ō" ASCII conversion errors at one moment.

(The sooner a beginner embrace Hiragana and Katakana, the better)