Yes, Most viburnums such as 'Winterthur' fruit best when cross-pollinated by another plant. A viburnum can have perfect flowers and still not set fruit using its own pollen. A perfect flower means, having both male and female parts in the same flower. All that being said, your Viburnum nudum winterthur, should still produce flowers, but the flowers would be without fruit and seeds. I'm not sure why you are not getting flowers. Can you send a photo to me so I can see the plant in the growing area?