I had this issue, which turned out to be caused by lack of Kerberos ticket. So the user can access NFS mount after doing kinit.
Is there any way to let users access NFS mounts without a need to acquire Kerberos ticket?
Update: Please note that the NFS export is already mounted on nfsclient machine via /etc/fstab:
nfsserver:/home /homex nfs4 sec=krb5p 0 0
Maybe I misunderstood a concept of NFS+Kerberos but I only wanted nfsclient to authenticate to nfsserver (and vice versa) by Kerberos during the mount and after that I would like all local nfsclient users to access the mount locally as it was a local filesystem.