Tincture, from powdered herbs?

I have tinctured passiflora incarnata from my own dried and cut herb. I have made other tinctures from purchased cut and sifted herbs.

I accidentally purchased powdered passiflora incarnata recently. Returns are not allowed. Can I make a tincture from powdered herbs?

Absolutely. With a couple caveats. The first, is that you'll need to use a close to the same weight of herbal material as possible. That gets a little finicky, unless you have an idea of the weight you normally use, in the whole or chopped herb. Otherwise, you can probably get away with a close guesstimate. So, for example, if you normally fill a jar about half way with chopped, dried herb, a fair guess as to an equal or somewhat generous portion of powder, would be a scant 1/4 jar, or even a little less, if you normally pack it fairly tightly.

The other one is filtering. A layer of good, tight cheesecloth, for a first filter, followed by a filtering through a paper coffee filter would probably work. To get the most with the cheesecloth, I'd lay the damp cloth inside a colander, and start pouring, while gently scraping the powdered herb across the fabric, with the edge of a spoon. If you try to just skip the cheesecloth, you'll probably be working at it for a long time.

To clarify beyond any doubt, I would use the same amount of alcohol as I did when using the cut herbs? And 1/4 quantity of powder?

I'd put the herbs into the jar, & completely top it off with alcohol, seal and shake the daylights out of it.