Hi, I have same situation when trying to upgrade from Standard to Premium on Azure.

My error:

"ConflictWithNetworkIntentPolicy","message":"Found conflicts with NetworkIntentPolicy. Details: Subnet or Virtual Network cannot have resources or properties which conflict with network intent policy. x conflicts with Network Intent Policy z. Network Security Group doesn't have supporting Security Rule for Network Intent Policy Security Rule

Checked, rules, subnets delegation. Everything is on place but still failing when upgrading from Azure Portal. Any ideas what could be wrong ?