Nuget package未下载到Telerik.UI.for.Xamarin。当我选择Package Source Telerik Nuget时，出现错误

Unable to find package Telerik.UI.for.Xamarin with version (>= 2019.2.619.1)
 Found 1 version(s) in nuget.org [ Nearest version: 2015.3.1202 ]   

 [Telerik Nuget] Unable to load the service index for source https://nuget.telerik.com/v3/index.json.
 Response status code does not indicate success: 401 (Unauthorized).

我已在APPDATA的nuget.config文件中添加了凭据

<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <packageSources>
   <clear />
  <add key="nuget.org" value="https://api.nuget.org/v3/index.json" protocolVersion="3" />
  <add key="Telerik Nuget" value="https://nuget.telerik.com/v3/index.json" />
</packageSources>
 <packageSourceCredentials>
    <telerik>
      <add key="Username" value="*****" />
      <add key="ClearTextPassword" value="*****" />
   </telerik>
 </packageSourceCredentials>
</configuration>

请查看下面的屏幕截图了解更多信息

我还在Window cre manager中手动添加了https://nuget.telerik.com/nuget url和凭据。
如何解决此问题？