Not an apex domain
The domain 207-172-140-90.s8536.c3-0.slvr-cbr1.lnh-slvr.md.cable.rcncustomer.com is not the root of its zone.
Instead, try zone transfer on lnh-slvr.md.cable.rcncustomer.com .
Instead, try zone transfer on lnh-slvr.md.cable.rcncustomer.com .