Honored Contributor
Honored ContributorA newer license works fine with an older version of Quartus so I don't think you problem is related to the license.
Quartus is able to upgrade a project from an older version to a newer one (it usually prints a message saying it needs to upgrade the database) but it may not be so easy in the other direction. That said 11.1 and 12.0 can't be that different... Did you try to delete the project database before opening it with 11.1? Go in the project (make a copy first!!!) and delete the "db" and "incremental db" folders. Then try to compile again. When you say "fails the fitter", is it an internal error or a more meaningful error message?