To my knowledge the Railway’s Hobby status isn't the direct reason for rejection,it is often caused by technical barriers like subdomain restrictions (Google usually rejects .railway.app domains), crawler issues due to the service "sleeping" or hitting resource limits, and low content density common in smaller projects.
There are various way to check that:
AdSense Dashboard: Go to the "Sites" tab and click on your URL to expand the "Needs attention" or "Show details" section.

Email Inbox: Search for an automated email from Google AdSense with the subject line "Status of your AdSense application."
Policy Center: Click on "Account" then "Policy center" to see if your content (rather than your hosting) is the issue.

Crawler Access: Verify your site is reachable by visiting yourdomain.com/ads.txt in an incognito window to ensure Railway isn't blocking bots.