@kalebkemp 

Can you please check if this is not an access issue?:

SHOW GRANTS ON SCHEMA my_catalog.my_other_schema;

Also test if you can successfully run a query that access data from both schemas:

SELECT *
FROM my_catalog.my_schema.some_table
JOIN my_catalog.my_other_schema.some_table
ON <join_condition>;

If this query fails, it confirms that the issue is with access or configuration rather than the materialized view creation itself.

Can you also please share the complete com.databricks.sql.io.FileReadException stacktrace?