Zendesk API and PowerShell

$Username = "username@domain/token"
$Token = "kasjdfkljasdfkjds"
$params = @{
	Uri = "https://{subdomain}.zendesk.com/api/v2/requests.json";
	Method = 'Get';
	Headers = @{Authorization = 'Basic ' + [Convert]::ToBase64String([Text.Encoding]::ASCII.GetBytes("$($Username):$($Token)"));
	} #end headers hash table
} #end $params hash table
Invoke-RestMethod @params
$Tickets = $result.tickets
$Tickets

When using an API token to authenticate with the Zendesk API, the username should be followed by /token and then the actual API token. The format should be "{email_address}/token:{api_token}". It looks like you have the /token in the right place, but you might be missing the colon : before the actual token.
 
Here's the corrected code:
 
$Username = "username@domain.com/token"
$Token = "kasjdfkljasdfkjds"
$Base64AuthInfo = [Convert]::ToBase64String([Text.Encoding]::ASCII.GetBytes("$($Username):$($Token)"))
 
$params = @{
    Uri = "https://{subdomain}.zendesk.com/api/v2/requests.json"
    Method = 'Get'
    Headers = @{
        Authorization = "Basic $Base64AuthInfo"
    }
}
 
$result = Invoke-RestMethod @params
$Tickets = $result.tickets
$Tickets
 
Make sure to replace {subdomain} with your actual Zendesk subdomain, and ensure that $Username and $Token contain the correct values for your Zendesk account.
 
Also, note that $result is being used to store the result of Invoke-RestMethod, but in your original code, you didn't assign the result to the $result variable. I've added that assignment in the corrected code above.

Upon reviewing and checking some external documentation, I would recommend following these steps If you are experiencing authentication issues with Zendesk API in PowerShell Universal:
 

1. Ensure that the script is running in an environment where it has access to the internet and is not being blocked by any firewalls or network policies.
    
2. Double-check that the email address and token are correct. The email should be the one associated with your Zendesk account, and the token should be generated from the Zendesk Admin interface.
    
3. Make sure you are using the correct API endpoint for your Zendesk subdomain. Replace {subdomain} with your actual Zendesk subdomain in the URI.
    
4.  Ensure that you are encoding your credentials correctly. The $Username variable should include your email followed by "/token" and the $Token variable should be your API token.

Yes, those are two different tokens, one is API token and the other one is Oauth token. You can read about each approach here