Immediate Auth0 Logout on One Machine

When Auth0 logins immediately fail on just one machine (but work fine elsewhere), it often indicates something local on that specific system interfering with the Auth0 session flow. Typically, it's about cookies, system clock issues, or local security/privacy settings that invalidate the Auth0 session token right after it's issued.

Below are common causes and fixes:

1. System Clock / Time Mismatch

Symptom: If your computer's clock is significantly off (even by a few minutes), Auth0's tokens can appear expired or not yet valid.

Fix:

• Ensure your system clock is correct and in sync. On macOS, enable "Set date and time automatically" in System Settings → General → Date & Time.
• If you're in a corporate environment, verify NTP is not blocked or failing.

2. Browser Cookie or Session Blocking

Symptom: Auth0 relies on cookies to maintain session state. If your browser or an extension is blocking third-party cookies, local storage, or is set to "always private" mode, the token/cookie from Auth0 can't be stored—resulting in an immediate logout.

Fix:

1. Check browser privacy settings:
   • In Chrome:
     • Go to Settings → Privacy and security → Cookies and other site data
     • Ensure third-party cookies are not blocked, or whitelist your Auth0 domain.
   • In Safari:
     • Go to Preferences → Privacy
     • If "Prevent cross-site tracking" is enabled, it may block Auth0 cookies; consider turning it off or adding an exception.
2. Disable or reconfigure any ad-blockers or tracking blockers (e.g., uBlock, Ghostery, Brave shields, etc.) that might silently block Auth0 domains or cookies.
3. Try a different browser to see if the problem persists. If it works there, it's likely a browser privacy/cookie issue.

3. Firewall, Security Tools, or VPN/Proxy

Symptom: Some tools (e.g., Little Snitch, Lulu, antivirus software, corporate VPN/proxy) can block or modify traffic to/from Auth0 domains—thus breaking the login handshake.

Fix:

• Temporarily disable or reconfigure these security tools to allow Auth0 traffic (usually *.auth0.com).
• If you are behind a corporate VPN/proxy, verify that Auth0 endpoints are allowed and that TLS/SSL inspection isn't rewriting certificates or injecting headers.

4. Corrupted Network or System Configuration

Symptom: If there's a deeper network config problem on macOS (e.g., broken DNS or leftover network preference files), requests to Auth0 might fail or come from an unexpected domain/IP.

Fix:

• Flush DNS:

  sudo killall -HUP mDNSResponder
  
    •	Reset DHCP / network interface (if relevant):
  

Replace "Wi-Fi" with the network service name from:

networksetup -listallnetworkservices

sudo networksetup -setdhcp "Wi-Fi"

• Temporarily move/rename /Library/Preferences/SystemConfiguration/preferences.plist and NetworkInterfaces.plist to reset all network prefs (then reboot). Only do this if you're comfortable losing saved network settings.

5. Hostname Resolution Errors (e.g., /etc/hosts)

Symptom: If you've modified /etc/hosts or use custom DNS, requests for your-tenant.auth0.com could be incorrectly routed.

Fix: • Check /etc/hosts for any unusual entries related to your Auth0 domain. Remove or comment them out if present. • Verify your DNS server is set correctly and can resolve *.auth0.com.

How to Narrow Down the Cause

1. Try a Different Browser: If it works in Firefox but not Safari/Chrome (or vice versa), that points to a browser privacy/cookie setting.
2. Use a Different macOS User Account: Create a fresh local account. If Auth0 works there, it's likely user-level config (browser settings, firewall rules, etc.).
3. Disconnect from VPN / Security Tools: If turning them off fixes the issue, you've found your culprit.
4. Check the System Clock: Verify your date/time is accurate.

Key Takeaway

An immediate logout after a seemingly successful Auth0 login is almost always due to token validation failure—which, on a single affected machine, typically means time sync issues, cookie blocking, or local firewall/hosts manipulation. Adjust your environment—by changing browser privacy settings, syncing the system clock, or clearing out local misconfigurations—to resolve the issue.