Can't get Get-PnPUnifiedAuditLog working - Always empty results

[prossum]

Does anyone have any idea why I can't get any results from the Auditlog?
When I do a manual query on the M365 Compliant Center I do get results, however when I try to get something from the Auditlog from an Azure Automation runbook I get nothing.
This is what i do:

$servicePrincipalConnection = Get-AutomationConnection -Name $connectionName

Connect-MgGraph -CertificateThumbprint $servicePrincipalConnection.CertificateThumbprint -ClientId $servicePrincipalConnection.ApplicationId -TenantId $servicePrincipalConnection.TenantId

$siteURL = 'https://<my-company>-admin.sharepoint.com'

$ctx = Connect-PnPOnline -Url $siteURL -ClientId $servicePrincipalConnection.ApplicationId -Tenant $servicePrincipalConnection.TenantId -Thumbprint $servicePrincipalConnection.CertificateThumbprint -ReturnConnection

$logs = Get-PnPUnifiedAuditLog -ContentType SharePoint -StartTime (Get-Date).AddDays(-5) -EndTime (Get-Date).AddDays(-1)

if ($logs) {
    Write-Output 'Yes! - We got something'
} else {
    Write-Output 'No results :-( '
}

And I tried other content types as well. All with no results.
Oh, and yes, The service principal has all required API permissions.

What do I do wrong?