Can you describe how you get to that dialog?
It sounds like you’re trying to create a “New DB connection” entity, in which case the internal DB is not available.
To change the database type of an existing ApplinX Application repository:
Right Click the ApplinX application. Choose Properties.
In the Properties Tree, select “Repository”.
Check the “Database” radio button, if it’s not already checked.
If you have been working with a read-only database, a message will come up asking if you would like to import the entities from the read-only DB to the new database - Click YES.
The Internal DB should be selected be default - Click “Change DB” to select another type of database.