I have had similar experiances on the canal - I think we fish the same one
My next tactic when this happens - I have not tried it yet - is to use a popper - cast the popper as close to the Pike as you can without spooking it and then let it settle - the Pike should be a bit interested in it and it will know it is there - slowly start to inch the popper along and if the Pike shows any interest then really rip it back - with any luck the Pike's instincts should kick in and it will attack it - result!
Got to be said though not tried it yet but this was the advice I was given and will be trying it out the next time I am on the canal.
Other Pike I have absolutely no luck with are cruising pike - sometimes you see the beasts just sauntering along without a care in the world - going at maybe a walking pace - they look as if they are trying to get somewhere but are not in any hurry to get there - I have followed Pike along the bank for a hundred yards and trying to get them to take is impossible - I have tried casting directly at them, running up the bank and waiting on them with the fly in the water to ambush them with the fly as they go past - sure sometimes they will change direction and have a look at the fly but just saunter along - in fact when I think about it I have only ever managed to stop one of these sauntering pike - the beast leapt straight out the water looked me in the eyes and then spat the fly out - leavng me feeling like a chump. I think I may have foul hooked it in the mouth as I was trying to get the fly as close to it as possible.
You can get some big fat Pike in the canal.