Adsense in Next.js

Anyone have success running AdSense ads on their Next js site? I've added the ads.txt file in /public as per Google's instructions and keep getting a 404 when I visit mydomain/ads.txt

When I replaced ads.txt with other static files n my public folder it works so wondering whether this is a Vercel specific issue.

I am aware AdSense takes time to crawl through to the page, but I can't even full up the txt file for now.