Q.jasmine sambac problem
I have a potted J. Sambac Grand Duke of Tuscany that has lost all leaves over winter in an unheated sunroom (temp kept 60-65). Many stems still strong and green. Checked root ball, no mushy roots but not white either. Repotted in smaller pot. Anything I can use to help the leaf buds swell to make new leaves? Looks like whatever tries to grow is all brown.
I would start introducing sunlight and warmer temperatures to your plant to try to wake it up.
Here are some articles that will help you.
https://www.gardeningknowhow.com/ornamental/flowers/jasmine/growing-jasmine-indoors.htm
https://www.gardeningknowhow.com/ornamental/flowers/jasmine/winterizing-jasmine-plants.htm