my daf lf wont start?

hi there..i have a daf lf on an 02 plate..ive got a starting issue where a relay just clicks behind the dash when the key is turned.it started this morning but then i stoped it and it then wouldt go again.. did exactly the same as i just mentioned... im not sure could it be the the safety solinoied in the gear box sticking.. or could it be an earth issue... all help really appreciated