Not an apex domain
The domain 64-121-50-223.s5341.c3-0.tlg-cbr1.atw-tlg.pa.cable.rcncustomer.com is not the root of its zone.
Instead, try zone transfer on atw-tlg.pa.cable.rcncustomer.com .
Instead, try zone transfer on atw-tlg.pa.cable.rcncustomer.com .