How can I add an external table to a semantic model

Hey Faric experts,

I have an external table called readartifact created from a Delta table and I have the Sync the default Power BI semantic model option turned on. However, I can't see this table in the default semantic model nor I can add it to a new semantic model. Please see the screenshot below. The readartifact table does not appear in the list of tables. 
Also the model view button is greyed out in the SQL endpoint view. 

Is this a bug or am I doing something wrong here?