Tree with yellow "sap", alive in front of and dead behind it.
Your Atlantic Weeping Cedar tree is definitely under stress. We can't say for sure why, as there may be multiple factors, but its placement close to the reflected heat of the fence would play a role. The dead areas can not regenerate. Prune them out.
If the tree is important to you, we'd suggest an on-site consult with a certified arborist, who is a tree health expert credentialed by the International Society of Arboriculture (ISA) to assess all factors.
You can search for one at www.treesaregood.org