When running a PowerShell script, you could get the following error:
"a.ps1 is not digitally signed. You cannot run this script on the current system. For more information about running scripts and setting execution policy, see about_Execution_Policies at https:/go.microsoft.com/fwlink/?LinkID=135170."

How to fix it? Run the following command:

Set-ExecutionPolicy -Scope Process -ExecutionPolicy Bypass

This command sets the execution policy to bypass for only the current PowerShell session after the window is closed, the next PowerShell session will open running with the default execution policy. "Bypass" means nothing is blocked and no warnings, prompts, or messages will be displayed.