🧩 The Problem

Recently, I recently enrolled in thinkit.club where I encountered a strange issue:

The course video I was trying to watch refused to load on my home Wi-Fi, but worked perfectly when I switched to mobile data.

When I inspected the browser's developer console, I found this repeated error:

ERR_NAME_NOT_RESOLVED

This told me the browser couldn't resolve the CDN domain name, which in this case was something like:

67c5a06699c28e491bb3321c.storage.fermion.app

That’s a classic DNS resolution failure — the system doesn’t know how to find the server address.

🔍 Investigating the Cause

I checked my network configuration and noticed that my router’s DNS settings were set to:

DNS Option: From ISP

This meant my network was relying on my Internet Service Provider’s DNS servers. These are often fine, but in this case, they were either outdated, misconfigured, or actively filtering certain domains — including the video CDN.

Meanwhile, mobile data (which uses the telecom’s DNS) had no such issue.

✅ The Fix: Use Public DNS

I changed the router’s DNS setting to:

DNS Option: Set Manually

And entered the following public DNS servers:

Primary DNS: 1.1.1.1 (Cloudflare)
Secondary DNS: 8.8.8.8 (Google)

After saving and restarting the router, I reconnected my device to Wi-Fi — and the video played instantly. 🎉

🔐 Why Public DNS Is Better

Public DNS services like Cloudflare (1.1.1.1) and Google DNS (8.8.8.8) are:

Faster due to global edge caching
More reliable with fewer outages
Privacy-respecting (especially Cloudflare)
Rarely block or misresolve domains

🌐 Want to Try It Yourself?

🔗 Cloudflare DNS - 1.1.1.1
🛠️ It even has apps for Android, iOS, and desktop!

💡 Final Thoughts

This issue was a reminder that network-level settings can silently break critical functionality — and debugging isn't always about code!

If you ever face unexplained resource loading failures (ERR_NAME_NOT_RESOLVED), try switching your DNS before going down a rabbit hole of browser or application debugging.

Have you ever debugged a similar issue? Let’s discuss in the comments.

🚧 How I Fixed a Course Video Playback Issue Caused by DNS Misconfiguration