I have not ever made a connection to a Crate.io database, however, I have successfully used the Generic adapter many times. As you know, it is not possible to test that adapter with all the existing databases so it is possible that something does not work with some of these databases. When I have to connect to a database which is not supported by the Denodo Platform I use the Generic adapter selecting at the same time the "Choose automatically" option. This option should help the Denodo Platform to find the most suitable adapter to connect to that database. In addition, if after doing that you still get an error I would suggest trying to create a base view from a sql query.
Hope this helps!