Chocolaty packages not installing via OneGet/PackageManagement in Windows 10?
The answer - I wouldn't use the OneGet Chocolatey provider until you hear an official announcement that it is up to date and no longer using the early CTP preview that came out in April 2014 (not a typo).
Until then you should continue to use the official choco client.
As mentioned in comments, I also tried to fix the problem by running Set-ExecutionPolicy Unrestricted in PowerShell, but I was still having problems with forbidden TLS/SSL security protocols.
And then (as mentioned) I tried through CMD-> %SystemRoot%\System32\WindowsPowerShell\v1.0\PowerShell.exe
and then in PowerShell :
> Set-ExecutionPolicy Bypass -Scope Process -Force; [System.Net.ServicePoin tManager]::SecurityProtocol = [System.Net.ServicePointManager]::SecurityProtocol -bor 3072; iex ((New-Object System.Net. WebClient).DownloadString('https://chocolatey.org/install.ps1'))
No more problems with TLS/SSL SecurityProtocol.