My dog wont walk go for a walk?

Ever since bonfire night last year my dog hasn't wanted to go on walks, sometimes, other times he will go fine. He is a two and a halve year old Cocker Spaniel, who used to go out 3 times a day, now he's struggling to get one. He will go on the garden fine and play around but most of the time when you put his harness and lead on he wont walk out the door or gate. We have tried treats, toys, new collars and harnesses but nothing seems to get him out. Please help, because I miss our walks and i'm sure he does too!