I am owner of server, all plugins are working except vanish.   I type in oxide.grant user Syntax permission and i get "permission doesnt exist.  I tried the same thing with "vanish.use" on the end and i got Permission 'vanish use' doesnt exist.  I tried with my steam ID and got the same messages.   I tried /vanish in chat, it tells me "you do not have permission for that.   I looked at console logs, everything appears to have loaded correctly.  I deleted and reinstalled and same thing.   This is my first try and using mods so im sure im missing something but i need help.

So I just set up my server a few weeks ago and was having trouble understanding the permissions also. For Vanish to work, you have to grant them individually.
So
oxide.grant <user or group> <name or steam id> <permission>
So these are these are the available permissions you can grant to a player or to a group (like an admin group):
vanish.allow
vanish.unlock
vanish.damage
vanish.permanent

oxide.grant user Greg vanish.allow
oxide.grant user Greg vanish.unlock
oxide.grant user Greg vanish.damage
oxide.grant user Greg vanish.permanent

Hope this helps you out.