SharePoint Sites throwing 404 Page not found error

If all SharePoint sites are returning 404 errors, including Central Admin site after a fresh installation. the problem might be the IIS setting about unlisted file extensions.

To check if this is the case:

Enable IIS logs and check the sub status of the 404 error.

If the sub status is 7 (i.e. error is 404.7), then check the IIS config file located at C:\Windows\System32\inetsrv\config\applicationHost.config

look for the segment

<fileExtensions allowUnlisted="false" >
and change it to

<fileExtensions allowUnlisted="true" >

this setting (false) basically only allows IIS to return the specified file extensions and will block any other files. Setting it to true may fix the 404 error.