I am a TrueNAS newbie myself, so consider that when reading my adviceā¦ 
I see that the /mnt/main/dados directory is owned by root/root with no read privileges outside the group. Although 3001 may have permissions for the share as a whole, I have found that if individual files or directories have more restrictive permissions the client will not be able to see them. Is there a reason that the owner must be root? Maybe try changing so the owner (or at least the group) is the 3001 one. Not sure why it would work with SMB, but maybe the user that your are logging into with is a member of root group.