Q.Damage to weeping cherry…unknown cause
My weeping cherry is 3 yrs. old. It bloomed beautifully the last 2 yrs. but this year it didn’t bloom at all and there are only sparse leaves on 1/2 the tree. We live in northern Ohio, just south of Cleveland and had a terrible winter w/ wind chills -40 at times. The branches on the 1/2 of the tree w/o leaves are still viable ( not dry or brittle) but the buds are not developing. Is this frost/freeze damage? What, if anything, can I do to save the tree?

Yes, in all probability, your tree is suffering from winter damage. A late freeze could have killed the buds on the less protected part of the tree. TLC and some pruning should help your tree recover, although sometimes it takes 2 or 3 years to get back where it was before the freeze. Here are a couple of articles on care and pruning: https://www.gardeningknowhow.com/ornamental/trees/weeping-cherry/weeping-cherry-growing-tips.htm
https://www.gardeningknowhow.com/ornamental/trees/weeping-cherry/pruning-weeping-cherry.htm