Sync networking configuration for Azure App Service hosting plan with Azure SQL Managed Instance
It might happen that although you integrated your app with an Azure Virtual Network, you can't establish a connection to SQL Managed Instance. Refreshing, or synchronizing, the networking configuration for your service plan can resolve this issue.
Sync network configuration
To do that, follow these steps:
Go to your web apps App Service plan.
Select Networking and then select Click here to Manage.
Select your VNet and click Sync Network.
Wait until the sync is done.
You are now ready to try to re-establish your connection to your SQL Managed Instance.