Fix HTTP Proxy Access Denied 0XC0020064 Error

Cause 1: Stale or Corrupted Proxy Cached Credentials

This is the number one cause. I've seen it hundreds of times. Windows caches your proxy login credentials, and when they expire or get corrupted, you get 0XC0020064. The machine tries to use old creds, the proxy says nope, and you're stuck.

Fix: Clear Credential Manager and Restart

1. Open Control Panel → Credential Manager.
2. Click Windows Credentials.
3. Look for any entries under Generic Credentials that mention your proxy server address or http://proxy names. Delete them all.
4. Open a Command Prompt as admin and run:

ipconfig /flushdns
netsh winhttp reset proxy
netsh int ip reset

Reboot. Test your connection. If it still fails, you might need to re-enter proxy credentials when prompted—or configure them via script if you're on a domain.

Cause 2: Wrong Proxy Server Address or Port in Windows Settings

Someone fat-fingered the proxy address. Or IT changed the proxy server and didn't tell anyone. This is more common than you'd think. The error 0XC0020064 will pop up when your machine tries to connect to a non-existent or unreachable proxy.

Fix: Verify Proxy Settings in Windows and IE

1. Open Settings → Network & Internet → Proxy.
2. Check Use a proxy server. The address and port should match what your IT department says.
3. Also check Internet Explorer (yes, IE, because Windows still uses its proxy settings for many apps). Open IE → Internet Options → Connections → LAN settings. Uncheck Automatically detect settings and make sure the proxy address is correct.
4. If you're not sure what the correct proxy is, run this command to see what Windows is actually using:

netsh winhttp show proxy

If it shows a proxy you don't recognize, reset it with netsh winhttp reset proxy and try direct access. If direct access works, you know the proxy settings were wrong.

Cause 3: Group Policy Overriding Manual Proxy Settings

On corporate machines, Group Policy often locks proxy settings. You can change them all day long, but the policy will revert them. The 0XC0020064 error appears because the enforced proxy is wrong or unreachable. This one's a pain because users can't fix it themselves.

Fix: Run rsop.msc to Identify the Policy

1. Press Win + R, type rsop.msc, hit Enter. This shows Resultant Set of Policy.
2. Navigate to Computer Configuration → Administrative Templates → Windows Components → Internet Explorer → Internet Control Panel → Proxy Settings.
3. Look for policies like Make proxy settings per-machine or Disable changing proxy settings. Note the exact policy name and the forced proxy address.
4. If the proxy in the policy is wrong, you'll need to contact your IT admin to fix it. There's no bypass—don't try to remove local policy files. You'll break something.
5. As a temporary workaround, you can use a PAC file if your admin allows it. In the proxy settings, check Use automatic configuration script and enter the PAC URL from IT.

If you're the admin, check your GPO in Group Policy Management Console under User Configuration → Preferences → Control Panel Settings → Internet Settings. That's often where proxy settings get pushed incorrectly.

Quick-Reference Summary Table

One last thing: if none of these work, check if your antivirus is intercepting proxy traffic. I've seen McAfee and Symantec cause 0XC0020064 more than once. Temporarily disable the AV's web protection module to test. If it fixes the error, update the AV or reconfigure its proxy exclusion list.