The database that is named in the DATABASE section of the form could not be opened. Either it could not be found, or your account has not been granted CONNECT privilege for it. You can use Informix SQL to separate these cases. Use Select option from the Database menu. If database-name is listed, the database can be found but could not be opened.
The database server looks for a database first in the current directory and then in directories that are named in the DBPATH environment variable. Check to see if database-name.dbs exists in one of those directories.