"Internal Server Error - The object 'vim.ResourcePool:resgroup-xxxxxx' has already been deleted or has not been completely created"VMware Cloud Director 10.6.1
This is caused by stale resource group entries which are left in VCD database post deletion of the resource group in vCenter.
Deleting Cloud Director's resource pools in vCenter directly is not a supported action as this could leave stale entries in VCD database.
You can detect and Fix Resource Pool Mismatches between VMware Cloud Director and vCenter by following this documentation:
Detect and Fix Resource Pool Mismatches between VMware Cloud Director and vCenter
If the above documentation does not fix the Issue, please contact technical support and note this KB in the problem description. For more information, see How to Submit a Support Request.