כִּ֣י לֹ֧א יָכְל֛וּ לַעֲשֹׂת֖וֹ בָּעֵ֣ת הַהִ֑יא כִּ֤י הַכֹּהֲנִים֙ לֹֽא־הִתְקַדְּשׁ֣וּ לְמַדַּ֔י וְהָעָ֖ם לֹא־נֶאֶסְפ֥וּ לִֽירוּשָׁלִָֽם׃
For they could not keep it at that time, because the priests had not sanctified themselves in sufficient number, neither had the people gathered themselves together to Jerusalem.
Read midrashic interpretation of II Chronicles 30:3: and classical rabbinic exegesis.