It sounds like your PC is not recognising that the dongle is attached.
As you already have the Mentor Licensing Utility loaded, you can use it to check that the dongle is being seen. Select Setup > Test/Install Hardware Key Drivers. This will give you options to install (and remove) the driver software and to test the dongle.
If your PC cannot see the dongle, try another PC to determine if the problem is (a) the dongle or (b) your parallel port. (Occasionally, parallel ports are disabled in the BIOS.)
If it is a faulty dongle then it may need to be replaced; if so, contact your local office or distributor. Note that if Hyperlynx 6.1 was released before USB dongles were supported, then a USB dongle may not be an option.