Agree with everything the others have said. Definitely a river that is entirely dependent on tides and water level/weather. Incoming tide, anywhere above 3 on the weir cam, and first/last light.
If you want to fly fish there aren't that many great spots, but guys do very well on olive wooly buggers, definitely my go to fly if I were to flyfish for them.
When I was just starting out at that river I thought i was doing something wrong too, but the trick is not fishing there when the water is low! fish are really spooky and leader shy and will often go the opposite way when your presentation splashes the surface. If you insist on fishing when water is low, use a tiny piece of roe [pinky nail size], small hook and no more than a 6lb leader.