Hey Quinnfyre..How are you???
Stephanotis are indeed slow-growing..Got mine in the mid-90's..a little 6" cutting. I was going to toss in the late 90's when the plant did NOTHING, then thought, I can't do that!! So, I set in the upstairs bathroom, west window, and it finally grew.
So, yep, they are slow-growing, need humidity, and sun..As they mature they vine..Yours will eventually need a trellis or something to climb on.
I alternate fertilizers during growing season, May-Sept, acid-loving, then flowering. Still no flowers, lol, but it has grown foliage..
It's funny you mentioned going to a plant show, smelling Steph flowers, and noticed no fragrance..someeone posted the same question a few years ago..Every Steph I've smelled had a heavenly scent, but of what I recall, someone posted, there are types w/o scent.. I don't know if this is true or not, but possible???
Stephs flower in spring to early summer, so don't give up hope. How tall is your Steph? Would you say mature? Is it in its climbing stage yet? When young, they grow upright, but as the plant ages, it vines off. I don't know if pruning helps branch off, making more compact..I've considered pruning, but the idea cutting off a bud came to mind, so I chicked out..LOL
Perhaps someone here knows if pruning helps branch out one stem, and the best time to prune.
Did you allow soil to dry a bit between waterings? Stephs won't thrive if kept wet. Mine did the same thing yours did/does..water and a leaf yellows and fall off. It probably has a lot to do with our climates. Can you set outside in summer? If so, find a shady spot to start off..I'm going to place mine out this summer too, and pray it flowers next spring. LOL. Good luck..and hope all is well with you, Toni

I'm fairly certain it won't flower this year. It's quite small, has maybe four or five leaves and is about 4 in tall. It hasn't done that losing leaf thing since I let it dry WAY out, as in almost dead dry out... the leaves were thin, had no luster, and wrinkly. Decided to water it anyway, even though I thought it was done for, and to my surprise the leaves plumped up and got green and shiny again. That's when I decided to care for it again, figuring if it actually wants to live now instead of sulking and dropping leaves here and there and shrinking instead of growing... I'm game. It hasn't dropped a leaf since. Or maybe it likes being in the south window better than it liked being under lights. Whatever the case, it's improved, but I'm still waiting for some new growth to appear.

I guess I don't tolerate bratty plants. And it knows now : )