> ## Documentation Index
> Fetch the complete documentation index at: https://gcore.com/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# Common Setup Issues

This section describes common CDN setup issues and how to resolve them.

## 503 service unavailable

This error means that the CDN cannot reach your origin server.

Possible causes:

* The origin server is not accessible.
* The origin blocks CDN IP ranges.
* The origin port is incorrect.
* The resource has not been fully propagated yet.

Solution:

* Verify that the origin server is accessible directly (for example, via browser or curl).
* Allow CDN IP ranges in your firewall settings.
* Confirm that the correct origin port is configured (80 or 443).
* During initial setup, propagation can take up to \~20 minutes. Wait for resource propagation to complete, then retry the request.

For more details, see [5xx error: how to solve server issues](/cdn/troubleshooting/5xx-error-how-to-solve-server-issues).

## ERR\_TOO\_MANY\_REDIRECTS

This issue occurs when both the CDN and the origin enforce redirects, creating a loop.

Possible cause:

* Both CDN and origin redirect HTTP to HTTPS.

Solution:

* Disable the redirect on either the CDN or the origin side.

## Website downloads as file

This behavior indicates incorrect response headers from the origin.

Possible cause:

* The origin returns an incorrect `Content-Type` header.

Solution:

* Check and correct MIME type configuration on the origin server.

## SSL certificate errors (Let’s Encrypt)

SSL issues are often related to DNS configuration and certificate validation.

Possible causes:

* DNS changes have not fully propagated.
* Let’s Encrypt cannot validate the domain.

Solution:

* Wait for DNS propagation to complete (up to 24–48 hours).
* Retry certificate issuance after propagation.

For more details, see [An SSL certificate isn’t working: how to solve](/cdn/troubleshooting/an-ssl-certificate-isn-t-working-how-to-solve-to-issue).