Cannot login using ServicePrincipal: Application was not found in the directory

I'm trying to set up an automation script that allows me to start up and shut down virtual machines in Azure without any user input. I've created an application registration (Web app / API) in Azure AD and in Subscriptions I've assigned the Virtual Machine Contributor role.

 

The application ID is: a8faf7f8-a0c2-4c03-8989-0a2d32915cd9

The tenant ID is: 696c6a65-a325-4af4-bfc4-f67a88425e4b

 

I have assigned a credential to the ServicePrincipal:

New-AzureRmADSpCredential -ServicePrincipalName https://mydomain.com/0f7b7873-2354-48ad-9ee4-9e6cfefd04d4 -Password "mypassword"

I try to log in as follows:

 

 

$applicationid ="a8faf7f8-a0c2-4c03-8989-0a2d32915cd9"
$principalPassword = ConvertTo-SecureString "mypassword" -AsPlainText -Force
$psCred = New-Object System.Management.Automation.PSCredential($applicationid, $principalPassword)

Login-AzureRmAccount -Credential $psCred -ServicePrincipal -TenantId 696c6a65-a325-4af4-bfc4-f67a88425e4b

 

But when I do, I get the following error message: Login-AzureRmAccount : AADSTS70001: Application with identifier '8faf7f8-a0c2-4c03-8989-0a2d32915cd9' was not found in the directory 696c6a65-a325-4af4-bfc4-f67a88425e4b

I am 100% sure that both the Application ID and Tenant ID are correct. What am I doing wrong?