。
Thank you for everything on that occasion.
Literal
That occasion [topic-は] various-things thank-you [polite-ありがとうございました].
Another その節 set phrase — here pairing with いろいろありがとうございました, the polite past-tense thanks form for a completed interaction. Together these form a common business/social set piece: 'Thanks for everything back then.' いろいろ 'various / lots of things' vaguely acknowledges many unnamed favors; a characteristic Japanese gesture to avoid specifying which you're grateful for.