Probably me being thick, but I am unable to set a valid offense. First time player and have looked at the rules and can not find out why.
Current selection that I have made is

Player Position Position
QB Quarterback
RB Halfback(Centre)
WR Wide Reciever (Right)
WR Wide Reciever (Left)
TE Tight End (Left)
RB Fullback (Right)
5 OLs on the line each taking one of centre, tackle and guard

Any advice would be much appreciated.

You have 12 players on offense, that's why...

Zeb123 wrote: Definately count 11 players As said look for people playing 2 positions on Offence or and injured player. I had the same where my lb was also playing CB.

Thank you, had managed to put my wide receiver down for both left and right by accident. I said it would end up being a silly mistake.