Not Dead But No Leaves
I am guessing that the attached PW Blue Chiffon - Hibiscus syriacus 'Notwood 3' suffered some kind of shock over the winter as it was given to me in January and I placed it outside against my shed out of the wind and loosely covered the pot. So it was not properly healed in. The twigs bend and have green coloring on them and I cut into 2 of the stems at the top and bottom of the bush and they are green inside but not a leaf in sight. I am wondering if I can give it a season and if it might rebound next spring? I have attached pictures.
Shrubs cannot go dormant for a year and then recover. You may see some green tissue, but it may just be dying slowly.
If any root system survived, it may not be able to support the huge top growth. If you cut it back severely, it may be able to put out enough foliage to recover. It may be a slow process but worth waiting to see what happens.
Meanwhile, pull the mulch away from the base of the shrub. Mulch should never touch the base of trees or shrubs, or be piled on their bark. Pull back a few inches. Keep mulch to 2-3" or less.
The flare at the base of the shrub should be above the soil line also.