Possible things to consider:
Azure SQL Managed Instance address
The Azure SQL Managed Instance address is entered on the Azure SQL Managed Instance | Connection Details screen. In the Spotlight Client, click Configure | Connections and select the Azure SQL Managed Instance connection type; right click on the connection and select Properties.
Check the address is a valid server name, server instance name or IP address.
For a Microsoft Cluster Server (MSCS) use the virtual name of the cluster.
Authentication
Authentication to the Azure SQL Managed Instance is defined on the Azure SQL Managed Instance | Connection Details screen. In the Spotlight Client, click Configure | Connections and select the Azure SQL Managed Instance connection type; right click on the connection and select Properties.
The connection will fail if the account permissions are insufficient to allow Spotlight to collect the data it needs.
When Use Diagnostic Server credentials is selected then the account running the Spotlight Diagnostic Server is used to connect to the Azure SQL Managed Instance. Ensure this account is trusted by the Azure SQL Managed Instance.
When filling in the User and Password fields, ensure the database user has sufficient account permissions to retrieve performance data from the Azure SQL Managed instance and host by WMI. Typically the account will be a member of the sysadmin server role. It could be an Azure SQL Managed Instance login (such as ‘sa’). Alternatively an account can be configured with the necessary privileges as documented in the online help.
Connection
The connection to the Azure SQL Managed Instance host is defined on the Azure SQL Managed Instance | Connection Details screen. In the Spotlight Client, click Configure | Connections and select the Azure SQL Managed Instance connection type; right click on the connection and select Properties.
Verify the Azure SQL Managed Instance host is in a domain. Spotlight cannot monitor an Azure SQL Managed Instance database when the Windows host is in a workgroup.
WMI Operability
Verify WMI is working and returns data properly. If WMI queries fail then a Windows Connection Failure alarm is raised on the third successive failed attempt, not on every failed attempt.
Verify TCP port 135 is open on the Windows server host.
UDP port 1434
If the Azure SQL Managed instance is hosted on a Windows server and UDP port 1434 is closed then the port number must be included in the address used to connect Spotlight to the Azure SQL Managed instance.
Microsoft Data Access Components (MDAC)
You may need to upgrade Microsoft Data Access Components (MDAC) on the Spotlight Client host AND the Spotlight Diagnostic Server host. More information is available from the Microsoft Download Center (search for MDAC).
Azure SQL Managed Instance availability
Verify the Azure SQL Managed instance is available and accessible over the network.
Configuration
If this alarm is raised too often or not enough for a given Azure SQL Managed instance you can configure certain parameters. See Configure Connections.