我花了一天的时间，试遍了这里的一切。 对我来说，我没有在Visual Studio中更新我的密码!

I had changed my work Microsoft account password last week or so, I also use that account to login to visual studio, however I wasn't prompted to update it and was not logged out of Visual Studio, it remained logged in. When I clicked on my initials in the top right of visual studio > Account settings > under All Accounts the work account had yellow exclamation triangle warning sign next to it, updated the new password, then updated some packages, dotnet restore, cleaned & rebuilt and the errors are gone.

在我的例子中，我只是重新启动docker并工作。

当我试图浏览NuGet包时，我得到了同样的错误，以解决以下相同的步骤:

1-转到%appdata%\NuGet\NuGet.config

2-验证该配置中提到的url

3-删除不需要的url

4-重新启动visual studio并检查

在Windows 7上测试

步骤1:打开命令窗口(运行cmd) 步骤2:如果TLS 1.2被禁用(添加注册表项)，执行以下命令启用TLS 1.2支持:

"HKLM\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\TLS 1.2\Client" /v DisabledByDefault /t REG_DWORD /d 0 /f /reg:32 reg add "HKLM\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\TLS 1.2\Client" /v DisabledByDefault /t REG_DWORD /d 0 /f /reg:64 reg add "HKLM\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\TLS 1.2\Client" /v Enabled /t REG_DWORD /d 1 /f /reg:32 reg add "HKLM\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\TLS 1.2\Client" /v Enabled /t REG_DWORD /d 1 /f /reg:64

我在Visual Studio 2015上执行Install-Package Modernizr时遇到了类似的问题。我通过以下步骤解决了这个问题:

Download the package from its online source. Go to Tools/NuGet Package Manager/Package Manager Settings. Select Package Sources from the window. Add a new package source by clicking on the + sign. Enter a name and source location by clicking on ... (triple dot) sign. Make sure that only the package source that you've just added is checked. Uncheck all the other package sources. Go to Package Manager Console and type Install-Package Modernizr. Visual Studio 2015 installs the package automatically and creates Scripts and packages folders in your root folder.

我希望同样的解决方案在安装其他包时也能起作用。

我有这个错误，然后我意识到我是用我的个人微软帐户而不是我的工作帐户登录的。

希望这能有所帮助。