Q.Flame Vine Leaves Are Shedding
getting full sunlight, grown in big pot, it’s been one year.. not even one feet grown

Certified GKH Gardening Expert
Most problems with this invasive species will come down to overwatering. They are not tolerant of this issue, and are very drought tolerant.
You may need a fungicide, and to correct watering habits. This article will help you with fungicide use:
https://www.gardeningknowhow.com/garden-how-to/info/using-fungicides-in-garden.htm
This article will help you with the care of the plant: