oh no

Author: rongxin-liu

cs50.dev.md

@@ -163,6 +163,32 @@ If on a corporate or school network that blocks any of the above, you might need
 
 ## Troubleshooting
 
+### I'm seeing "Oh no, it looks like you are offline" error message.
+
+First of all, make sure all the required [domains](/#domains) are not blocked by your device or internet environment.
+
+Check that you have a stable internet connection and that your company network is not blocking the connection. If possible, check logging for rejected connections on your device.
+
+If you see rejected connections, make sure the domains documented by the `/meta` REST API endpoint are not blocked by your firewall. For more information, see ["REST API endpoints for meta data."](https://docs.github.com/en/rest/meta/meta#get-github-meta-information)
+
+You can run this command in your terminal to get the list of domains required by GitHub Codespaces:
+
+```bash
+curl -L \
+  -H "Accept: application/vnd.github+json" \
+  -H "Authorization: Bearer <YOUR-TOKEN>" \
+  -H "X-GitHub-Api-Version: 2022-11-28" \
+  https://api.github.com/meta
+```
+
+Follow [this instruction](/github/#personal-access-token) to generate a GitHub personal access token.
+
+Alternatively, to get the list of domains required by GitHub Codespaces, execute the following command using GitHub CLI:
+
+```bash
+gh api meta | jq .domains.codespaces
+```
+
 ### How to monitor global variables in debugger
 
 In debug50's **RUN AND DEBUG** pane, there's a section labeled **WATCH**. You can add expressions to this section, and the debugger will show you the values of these expressions as you step through the program. The expressions can include global variables and array names.