Hi,
Hoping someone might be able to give me a hand with this as I
I have found the solution for me anyway, basically there is a setting in sudo :-
Defaults requiretty
I commented this out so that nagios can run without a tty. Just have to figure out what the correct setting should be as I don’t want anyone to be able to run sudo without a TTY 
Thought I should post my findings as I have found alot of people with a similar issue to me with no answers