If you want customers to place tickets on a given queue, that customer should have permissions under the group that queue belongs to, so please go to /otrs/index.pl?Action=AdminCustomerUserGroupand give permissions accordingly.
Without this configuratin customers should have access to all queues ... so this is not the solution ...
An, is there an error in the OTRS log file?
Can you select the Queues in the Agent Interface, e.g. in the Phone-Ticket view?