Cannot change the manual proxy setting in Windows 10

Finally I found a 100% working solution. Here are the steps :

Possible Causes : Avast antivirus, Browser safeguard, 127.0.0.1:8080/proxy.pak file, windows registry error…

How to remove :

1. First of all try all the things mentioned by Darwin Dim in his answer. For most cases those steps will do the work and you need not to go any further .
2. If the problem still exists then download Malwarebytes Anti-malwareand do a full scan of your PC. In our case it worked very well and found some other malware too. Recommended even if you don’t have any problems.
3. If the problem is still there then here is your last option → Take out your important files and Hard reset your PC with ‘Remove Everything’ option. Do not use ‘Keep my files’ option.

Hi John,

Regarding the default proxy that's set on your device, this can be caused by a browser extension that's embedded on your system settings. Considering the steps that you've performed, the next step that we recommend is to manually change the set up via registry edit. To do this, follow these steps:

1. Press Windows + R key to open the Run command.
2. Type in regedit and click OK.
3. Follow this folder path HKEY_CURRENT_USER/Software/Microsoft/Windows/CurrentVersion/InternetSettings
4. Under the InternetSettings folder, locate ProxyEnable. Right-click and select Modify to change Value Data from 1 to 0.
5. Locate the ProxyServer key and check if the proxy that's causing the error is present under the Data column. If yes, right-click on the ProxyServer key and select Delete.
   

Disclaimer: Make sure to properly follow the steps provided, since editing the registry can affect the system directly and can cause serious consequences that can prevent the system from starting correctly.

Do post back if you encounter any challenges along the process.