The error message “Your SharePoint admin doesn't allow site owners to update app permissions. Please contact your SharePoint administrator." is displayed when trying to perform the “Register Client ID and Client Secret” in the admin guide when configuring AutoPull of documents. This is caused by enhancements Microsoft made to the security measures and administrative governance on SharePoint.

To resolve the issue, the SharePoint admin needs to execute the following commands in PowerShell to allow the required access. Please update the text marked yourDomain as needed:

1.  Connect-SPOService -URL https://yourDomain-admin.sharepoint.com

2. Set-SPOTenant -SiteOwnerManageLegacyServicePrincipalEnabled $true


For more information, please see details from Microsoft:
SharePoint site collection admins can't register apps or update permissions