Lilacs not thriving in Victoria, BC, due to several reasons, including climate, soil conditions, sunlight exposure and watering practices. Here are some common factors to consider:

1. Climate: Victoria, BC, has a temperate marine climate, with mild, wet winters and cool, dry summers. While this climate is generally conducive to growing lilacs, if your specific location doesn't match the plant's needs for chill hours (cold temperatures required to break dormancy), it might affect their growth.
2. Soil Conditions: Lilacs prefer well-drained, neutral to slightly alkaline soil. If your soil is too acidic, too dense, or not draining well, it could hinder the plant's growth. Testing your soil and amending it based on the test results can help.
3. Sunlight Exposure: Lilacs require full sun to bloom profusely. If your plant is in a location that receives less than 6 hours of direct sunlight daily, this could be a contributing factor.
4. Watering Practices: Overwatering or underwatering can stress the plant and affect its growth. Lilacs do not like to sit in waterlogged soil, so ensure your watering schedule allows the soil to dry out somewhat between watering sessions.
5. Age of the Plant: Young lilac bushes may take a few years to establish themselves and start flowering. If your lilac is new, it may just need more time.
6. Pruning: Incorrect pruning can also affect lilac growth and flowering. Lilacs should be pruned right after they bloom to shape the plant and remove spent blooms. Avoid pruning them late in the season as you may inadvertently cut off next year's buds.
7. Pests and Diseases: Although lilacs are relatively hardy, they can be susceptible to pests and diseases like powdery mildew, scale, and borers. Check your plant for signs of distress and treat accordingly.
8. Variety: Some lilac varieties are better suited to certain climates and soil types than others. Ensure the variety you've planted is well-suited for the Victoria area.

If you're doing everything right and still not seeing growth, it might be beneficial to consult with a local horticulturist or extension service. They can offer more personalized advice and may help identify any specific issues with your plant.