it could be both. AD and DNS having issues....
let's see what the routing look like. and then we can go furter and see you have the correct firewall rules open for the correct interface by KB:
https://kb.netapp.com/app/answers/answer_view/a_id/1030571/loc/en_US
can you print the following please?
dns show -fields name-servers -vserver <SVM name>
cifs domain discovered-servers show -vserver <SVM name> # can remove everything that is not the address. and preference
network interface show -vserver <SVM name>
network route show -vserver <SVM name>
network connections active show -Print-ip-addresses -vserver <SVM name>
Gidi