Symptoms
In the Microsoft SQL Server 2017 Tabular Direct Query model, the data source that has MultiSubnetFailover=True;ApplicationIntent=ReadOnly properties doesn't route requests to AlwaysOn availability groups.
Status
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
Resolution
This problem is fixed in the following cumulative update for SQL Server:
About cumulative updates for SQL Server:
Each new cumulative update for SQL Server contains all the hotfixes and all the security fixes that were included with the previous cumulative update. Check out the latest cumulative updates for SQL Server:
References
Learn about the terminology that Microsoft uses to describe software updates.