Crimson glory vine vitis coignetiae producing loads of flowers, but the leaves are very small and don't cover our pergola as well as they used to.
Vines (any member of the Vitis species) need a good supply of nitrogen to support the leaf growth in particular. So I'd suggest giving it as good application of slow release general purpose fertiliser - or even one formulated for Citrus which will have a higher concentration of nitrogen. Adding some animal poo like chook or cow poo (once it has composted for a while to decrease the acidity) will also help. Rake it into the top soil around the root area taking care not to disturb the roots too much and ensure it is well watered in.