Tables without a clustered index are not supported in this version of SQL Server.
Some versions of Azure SQL require every table to have a Clustered Index. If you are using one of those versions of Azure SQL, you can run the following command to create an Index. Set the <tablename> to the same name you have entered in your MigrationWiz project.
CREATE CLUSTERED INDEX idx_auditlog on <table> ( MailboxId, EventTimestamp );
This will create the necessary Clustered Index and allow MigrationWiz to insert data into the table.