I think it is an outdoor plant that wants full sun.

What zone/location are you in?
I have one that spends all warmer days outside, in full sun. It bloomed non-stop, often few blooms at the same time. Maybe it's a very common variety-I don't know much about them otherwise-it was grown from a cutting. Inside for about a week now, and has few buds with 1 opened since yesterday. Will not look so great after the winter inside, but will survive. Likes the sun.
Rina

It looks like Passiflora suberosa, if so the flowers are tiny compared to other passionfruit flowers. Maybe it flowered but you missed them. The fruits are tiny also. As already mentioned passionfruit like it outdoors in full sun. They don't like an acid soil so a bit of liming might help.

I found full sun to be too much for my maroon
Passiflora suberosa.

I have two, one with maroon blooms & the other like
the one pictured above with purple flowers.
as a child I remember seeing the purple flowered
vines growing wild.
while mine will be in pots all winter...next spring I'll
plant them where they'll get morning & early afternoon
sun only. and east facing...because my neighbors
white flowering passion flower vine is doing so well
facing east. hers are planted directly in the ground,
she cuts them down every March & by June they are
growing all over the lattice work framing of her porch.
I hope to be half as successful at my plantings as
my neighbor is with hers...then I'll get a white cutting!!

best of luck.

I do have it under a grow light for about 12 hours a day and it seems to be doing a little better. I am hoping to keep it alive until next summer. I live in Colorado which I believe is 5b. Thanks everyone for your help.

Mine goes in a sunny window in winter but does gradually turn brown and die off. Then come Spring new shoots start and then it's about time for it to go back outside. So just keep it tidy, cut off dead bits and keep watching for bugs.