Hello @Lucca Toledo,
I understand that you are not able to find the application under the App registration blade even though the application is functioning.
- It might be that the application has only a Service Principal in the tenant, but the App Registration (Application Object) resides in another tenant.
Azure Portal -> Microsoft Entra ID -> Enterprise applications -> Search for your Application ID.
If you find the app under Enterprise applications then, it the service principal the App registration is not done in your tenant.
You can also make use of PowerShell to confirm:
# Search for Application object
Get-MgApplication -Filter "appId eq 'a0a7be11-2643-4208-a991-xxxx'"
# Search for Service Principal object
Get-MgServicePrincipal -Filter "appId eq 'a0a7be11-2643-4208-a991-xxxx'"
Let me know if any further queries - feel free to reach out!