git' is not recognized while using c# (web application)

I want to execute the power shell logic using c#(web application) but i'm getting the issue

The term 'git' is not recognized as the name of a cmdlet, function, script file, or operable program. Check the spelling of the name, or if a path was included, verify that the path is correct and try again.

I have added the git path in environmental variables and able to execute the same powershell logic from powershell window without any issues.

My powershell script:

function CheckoutTheCode($checkoutRepoUrl, $checkoutDirectory, $checkoutBranch)
{
    [hashtable]$Return = @{}
    try
    {
        # Cloning
        git clone --single-branch -b $checkoutBranch $checkoutRepoUrl $checkoutDirectory

        $Return.Status = $true
        $Return.Message = "Success"
    }
    catch
    {
        $Return.Message = $Error[0].Exception
        $Return.Status = $false
    }

    Return $Return 
}

$checkoutDirectory = "local directory for checkout"
$checkoutRepoUrl = "bit bucket repo url"
$checkoutBranch = "branch version"
CheckoutTheCode $checkoutRepoUrl $checkoutDirectory $checkoutBranch

My c# code:

using (PowerShell PowerShellInstance = PowerShell.Create())
{
    PowerShellInstance.AddScript("PowerShell script");
    Collection<PSObject> PSOutput = PowerShellInstance.Invoke();
}