Sites hosted by AWS unreachable for customers

This issue appears to be related to DNS resolution or network connectivity problems affecting a specific geographic area served by your ISP. Since the problem is localized to a particular region and impacts multiple AWS-hosted websites, it's likely a routing or DNS issue between your ISP's infrastructure in that area and AWS services.

Here are some troubleshooting steps to help diagnose and resolve the issue:

1. Verify DNS resolution by having affected customers run diagnostic commands like nslookup on the unreachable domains to see if they're resolving correctly.

2. Check if there are any backbone link failures or routing issues in the affected area that might be causing traffic to be redirected through suboptimal paths, resulting in connectivity problems or high latency.

3. Test if customers can access the sites using alternative DNS servers (like Google's 8.8.8.8 or Cloudflare's 1.1.1.1) instead of your ISP's default DNS servers.

4. Investigate if there are any network ACLs, firewalls, or other filtering mechanisms specific to that region that might be blocking access to AWS IP ranges.

5. Check if the issue is related to a specific AWS edge location or region that serves that geographic area, as there could be temporary disruptions affecting service delivery to your customers.

6. Consider reaching out to AWS Support to report the issue, as they may be able to provide insights about any known problems affecting service delivery to your region.

Since this is affecting multiple customers in a specific geographic area, it's likely an infrastructure or routing issue rather than individual customer configurations. Collecting detailed information about the exact error messages, traceroutes, and DNS resolution results from affected customers will help in pinpointing the root cause.
Sources
Internet outbound problem | AWS re:Post
Strange intermittent dns issue to access aws console/services | AWS re:Post
Resolve website access issues in Amazon Route 53 | AWS re:Post
AWS Edge Location EG CA Stopped Working | AWS re:Post

Hello! I'd recommend reaching out to the site administrators associated with each of these sites through their respective "contact us" pages so that they can verify the source of the issue from their end. AWS also offers a service health dashboard in case of AWS service-wide issues impacting connectivity - you can check the event history to see if the date range of the any events overlaps with when your customers reported issues (not sure if the issue is still ongoing or not).