New to TikTok ads, $150 spent, 0 conversions. Looking for advice

Hey everyone, I'm new to TikTok ads and could use some advice. I run a streetwear store (Shopify) and I'm used to Meta, where I consistently get 4–5x ROAS. On TikTok I've spent about $150 so far with zero purchases.
My setup:
Campaign: Sales → Website, ad group budget (ABO), $50/day
Ad group: 1 ad group, US, broad/automatic targeting, optimizing for Purchase, Maximum results bid strategy, 7-day click / 1-day view attribution
Pixel: Shopify TikTok app. Purchase event is active with an EMQ of 89, and the Pixel Helper extension says it's set up correctly
Ads (2):
Spark Ad of an organic video that went viral on our account
The same video re-edited with captions, uploaded as a regular ad
Landing page: homepage
Turned off all the auto-generated creative and smart creative features
Results so far (~3 days): about $112 spent on the Spark Ad, $38 on the captioned version, 0 purchases.
Is this normal for the first few days on TikTok? Should I be using a different landing page, different creative, or a different campaign type? Anyone coming from Meta who figured out what works differently on TikTok, I'd really appreciate your tips. Thanks!