AppData\Roaming\npm\react-native.ps1 cannot be loaded because running scripts is disabled on this system. For more information, see about_Execution_Policies at https:/go.microsoft.com/fwlink/?LinkID=135170.

=>run powershell as administrator
=>run foll command
get-ExecutionPolicy
=>if restricted; run following command
set-ExecutionPolicy Unrestricted
=>and set to all
=>again check by foll. command
get-ExecutionPolicy
**it will get unrestricted and problem is solved**

Set-ExecutionPolicy -Scope CurrentUser -ExecutionPolicy Unrestricted

//open windows command shell as administrator and run command
Set-ExecutionPolicy Unrestricted