If you have manjaro-settings-samba installed, that will create a default smb.conf. You will need to read the samba documentation to configure to your liking, eg. in Global section:
client min protocol = SMB2
With nautilus-share, if it is similar to thunar-shares-plugin…have you right clicked on folder(s) that you would like to share and chosen something to the effect of “share this folder”?
Check ownership of the folder(s) that you are trying to share. Make sure that folder(s) are owned by you as user and not owned by root.
See also similar post: