Here in services.conf: ServicesRoot "nick nick nick", make sure there are any # before the "ServicesRoot". Users cant use /botserv bot add, only Services Admin.
To give services access to opers (that has +o flag) you should take a look: /operserv help oper and /operserv help admin
Services will not start if ServicesRoot is commented out, nor will it start again after a restart. Nor will an /os reload be successful. So if OperServ is issuing Access Denied .. it's guaranteed not to be ServicesRoot being commented.
However, to gain access to any OperServ/NickServ/ChanServ/BotServ command that requires OperServ access you need:
1> identify to a registered nick that is on the access list. [ /os staff ]
2> you *must* be using a nick on the access list. [you must see a * next to your nick, in the output of /os staff]
3> must be /oper'ed with a global O:Line
4> You must have sufficient access to the command in question, this means that if you are trying to use /os set *, you must be Root