Without knowing exactly what you're doing for 3.5.14 to 4.0.0, one item suggested to me was that 4.0 does not access the 'dot' db (i.e. graph.db) as a naming conversion seen in previous migrations. I was told to get rid of the '.db' portion of the database name. I'm essentially asking the same question here...
If you are able to successfully migrate from 3.5. to 4.0 please share your steps.