Problem Description
When experiencing this issue after a website update or new package creation, DNS propagation delay is the likely culprit. The problem typically resolves within hours.
Root Cause Explanation
Your DNS resolvers have the lookup of www.domain.com stored in their cache from previous visits. When checking the non-www version, resolvers lack cached data and fetch the current IP address instead. This creates the disparity where one variant works while the other doesn't.
Solution
Users must wait for their resolver's cache to expire. Once the cache clears, subsequent visits trigger fresh lookups that retrieve the correct IP address. If using the provider's nameservers, this typically takes no longer than one hour.