Diagnosing Postman 'Could not get any response' Errors: Network and SSL Guide

Recognizable Condition

When you send a request in Postman and the response pane shows Could not get any response, the request never completed the TCP/TLS handshake. No HTTP status code is returned, so the problem lives at the transport layer — network routing, TLS negotiation, or an intermediary blocking the connection.

Cause / Diagnostic Quick‑Reference Table

Ordered Diagnostic Checks

1. Confirm the endpoint is reachable. Open the same URL in a browser. If the browser loads the page, the server is up and the network path works.
2. Inspect the Postman Console. Press Ctrl+Alt+C (Windows/Linux) or ⌘+Option+C (macOS). Look for low‑level error codes such as ECONNREFUSED, ETIMEDOUT, or UNABLE_TO_VERIFY_LEAF_SIGNATURE.
3. Test with a command‑line client. Run the following in a terminal (any user, no elevated rights required):

   curl -v --max-time 10 "https://{{TARGET_HOST}}/{{PATH}}"

   Replace {{TARGET_HOST}} and {{PATH}} with your actual host and path. Observe the verbose output:
   • SSL certificate problem → certificate verification issue.
   • Connection refused → nothing listening on the port.
   • Operation timed out → packet loss or firewall drop.
4. Check proxy settings. In Postman go to Settings → Proxy. Ensure Use system proxy matches your OS configuration, or define a manual proxy that matches the corporate PAC file. Test again after toggling.
5. Validate TLS version and cipher support. Some legacy servers only accept TLS 1.0/1.1. Add --tlsv1.2 or --tlsv1.3 to the curl command to force a specific version and see if the handshake succeeds.

Fixes Tied to Findings

SSL Certificate Verification Failure

If the curl test shows a certificate error, you have two safe options:

• Import the CA or self‑signed certificate into Postman. Settings → Certificates → Add Certificate. Provide the CRT/PEM file and the matching domain. This keeps verification enabled.
• Disable SSL verification only for the offending domain. In the request’s Settings tab, turn off SSL certificate verification. Warning: this opens a MITM vector; never use it for production traffic.

Proxy Misconfiguration

Correct the proxy entry to match the corporate PAC URL or explicit host:port. If you must bypass the proxy for internal hosts, add them to the No proxy for list (comma‑separated). Changing system‑wide proxy affects all apps; prefer the Postman‑scoped setting.

Firewall / Antivirus Blocking

Create an outbound allow rule for Postman.exe (Windows) or the Postman binary (macOS/Linux) on ports 80/443 and any custom API ports. Verify by re‑running the curl test; the error should disappear.

Protocol / Port Mismatch

Ensure the request URL scheme matches the listening service. If the server only serves HTTP on port 8080, use http://host:8080. Update the request in Postman accordingly.

Escalation Criteria

Escalate to network or security teams when:

• All local checks pass but curl still shows ETIMEDOUT from multiple workstations.
• Packet captures (Wireshark) reveal TCP SYN retransmissions without SYN‑ACK.
• Corporate policy mandates a managed proxy that Postman cannot authenticate against (e.g., NTLM/Kerberos). In that case, request a service account or a proxy‑auto‑config exception.

Limitations & Verification

Disabling SSL verification is a quick workaround but must be reverted before any production‑grade testing. Changing proxy settings can break other tools that rely on the system proxy. After applying a fix, confirm the request succeeds in Postman and the same curl command returns a 2xx status with a valid certificate chain (curl -v --cacert /path/to/ca.pem https://host/api).