Just closing the loop on the Q&A question here. Based on the support ticket you created I see it has been resolved now.
Issue description:
You experienced issues with the Network Manager and a linked VNET after attempting to delete them using Terraform. This resulted in the VNET and an IPAM pool being left in a failed state. When you tried to view the IPAM pool, you received a "failed to fetch usage data" message. Additionally, when you attempted to delete the VNET, you got a "can't delete as ipAllocation exists" error. Attempts to remove the IP allocation via AZ CLI also failed.
Solution:
This error was due to a known issue currently affecting IPAM in Azure Virtual Network Manager which is currently in preview. The backend team was able to remove the IPAM pool reference from your VNET following which you were able to delete the VNET.
A work around was also suggested by the product group that if anyone facing a similar issue can wait for 30 minutes after deleting the IPAM pool and then recreate the pool then disassociate their virtual network and static CIDR from the pool before attempting deletion again it should resolve their issue.
Please let me know if you have any questions. Thank you!
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