Hi @Feehan, Andrew,
Welcome to Microsoft Q&A Platform. Thank you for reaching out & hope you are doing well.
- Please clear browser history, cookies and cache and try with a different browser once.
- Try to use azure CLI/Powershell to deploy resource in azure as a work around.
- Please make sure that you have proper permissions to deploy a VNet in your Subscription level.
- Please try to get more information on Developer Console. Right click on the affected page go to inspects > Console and try to find any console errors.
- Try to disable the extensions, sometimes they interfere with the Azure portal. Try disabling extensions, especially those related to privacy or ad-blocking, and refresh the page.
- Try to check the Azure Service Health in the portal to ensure there aren't any ongoing issues with the networking services in your region.
Kindly let us know if the above helps or you need further assistance on this issue.
Please "Accept the answer" if the information helped you. This will help us and others in the community as well.
Regards,
Sai Prasanna.