Usually when there are plenty of lush leaves and no flowers, it can be the result of fertilizing with a high nitrogen food that encourages foliar growth at the expense of flowers. In this case, however, there are a few flowers but some of the lower leaves are yellowing showing only the green venation. Suggest you switch to a slow-release fertilizer formulated for blooming plants or an organic granular fertilizer. Also morning glory plants do best in full sun, at least 6-8 hours, and regular water especially in containers. Inspect the foliage and stems closely to see if there are signs of sucking insects such as scale, aphids or mealybugs as these suck the nutrients from leaves and stems. Suggest you show your photo to a local garden center for confirmation of the problem and remedies.