I have to mention this happened on windows 7 with powershell 2.0 and .NET < 4.5
We were getting the following traceback after Pkg.add("Anything")
Downloading artifact: OpenBLAS32
Exception setting "SecurityProtocol": "Cannot convert null to type "System.Net.
SecurityProtocolType" due to invalid enumeration values. Specify one of the fol
lowing enumeration values and try again. The possible enumeration values are "S
sl3, Tls"."
At line:1 char:35
+ [System.Net.ServicePointManager]:: <<<< SecurityProtocol =
+ CategoryInfo : InvalidOperation: (:) [], RuntimeException
+ FullyQualifiedErrorId : PropertyAssignmentException
Exception calling "DownloadFile" with "2" argument(s): "The underlying connecti
on was closed: An unexpected error occurred on a send."
At line:7 char:24
+ $webclient.DownloadFile <<<< ("https://github.com/JuliaBinaryWrappers/OpenBLA
S32_jll.jl/releases/download/OpenBLAS32-v0.3.9+4/OpenBLAS32.v0.3.9.x86_64-w64-m
ingw32-libgfortran5.tar.gz", "C:\Users\manuelma\AppData\Local\Temp\jl_zIYF4alXQ
A-download.gz")
+ CategoryInfo : NotSpecified: (:) [], MethodInvocationException
+ FullyQualifiedErrorId : DotNetMethodException
ERROR: Unable to automatically install 'OpenBLAS32' from 'C:\Users\manuelma\.jul
ia\packages\OpenBLAS32_jll\jNV1v\Artifacts.toml'
Stacktrace:
The solution was to install .NET 4.5 and Powershell > 3. This is mentioned in the platform specific instructions but I managed to miss it.