I think I can help with that, full sun is a great start for veronica plants as they do love the sunshine, but they also need decent soil and regular watering to bloom properly. Have you been fertilizing your plant at all, because veronicas are heavy feeders and need a balanced fertilizer to produce lots of flowers? Also, make sure you're not overwatering, as this can cause the plant to focus its energy on leaf growth instead of blooming. Maybe try pruning it back a bit to encourage new growth and see if that does the trick.
