If taking cuttings this time of year, choose firm hardwood cuttings with at least three nodes (four of five wouldn't hurt). You can plant the cuttings almost horizontally, with only the top node above ground level. Grow them in a frost-free location (garage/greenhouse/etc). Bottom heat (if growing outdoors) and rooting hormone can be beneficial.

BTW, when looking for info about propagation try using the scientific name (in this case Parthenocissus tricuspidata) along with the word cutting or the word propagation. I didn't spend time closely examining the results, but a quick google search (as described above) looked like you'd get plenty of good info.

cutting need three things [if not more] :

1 == a properly wetted media ... and the moisture must be maintained.. properly ... not too wet.. not too dry .. etc .. for the duration of the rooting ...

2 == proper light ... and the windowsill may or may not be sufficient for such ... and there is no way to tell from the facts ...

and finally, ...

3 == ambient humidity ... of which there are no facts ... w/o roots.. the plant must rely on the leaves to suck in enough moisture for the plant to survive.. until some roots develop ... this is as simple as a clear plastic bag... etc ... it is possible.. for it to shed all the leaves.. so as to maintain the buds under.. until roots develop .... its not the best world.. but it is still possible ....

all that said ... a 50% success rate is not all that bad ... you really dont expect 100%, do you???

if only a couple roots.. so be it.. and when they start getting leggy.. make some new cuttings ... etc .... presuming you are not working in a greenhouse.. you most likely have limited space.. so fear success .. lol ... you have a long time to hold over new rootings in z5 until the spring ....

i would start by insuring humidity.. if you have not been providing such

good luck
ken