Lipstick
plant is unlikely to bloom if it isn't a bit root-bound...so if you've been moving it to a larger pot every year that could be the problem. In the future, don't move to a bigger pot until the pot is full of roots, with not much soil left.
Also, what is your fertilizing regimen? Lipstick
plants should be fed with a food for blooming
plants...African Violet food is perfect as they're in the same
plant family, gesneriads. But don't over-do the fertilizing, dilute to half the dose recommended on package.
Karamy