Regular user can not access NFS4 mounts (permission denied)

Solution 1:

Kerberized NFS (any gss) requires Kerberos tickets. You'll have to use the much less secure sys security level if you want uses to be able to access NFS without tickets.

It would be better to have users acquire tickets when they log in. Ether by using sssd or pam_krb5 as part of you pam auth stack, or by credential delegation for ssh (i.e. GSSAPIAuthentication yes and GSSAPIDelegateCredentials).