You're using the incorrect lure size (too big or too small). Another typical reason why fish aren't biting is that you're employing lures and baits that are either too little or too large. Fishing with a large lure might be a costly error. Fish usually avoid lures that are too large because it's difficult for them to detect the movement of the lure.
Fish often stop biting because they're not interested in what you have to offer. If there's no food available, if there's nothing attractive about your bait, if it's too old or too new, if it smells bad or doesn't smell good enough - then why should they bother taking it off the hook?
The most common cause of fish stopping biting is that you're using the wrong size hook for the species of fish you're fishing for. Some fish are picky about the type of material used to make their hooks, while others will simply refuse to bite at all if the hook isn't properly sized. Knowing how to correctly select a hook size can mean the difference between success and failure when fishing for trout, bass, salmon, etc.
Fish also stop biting if they feel threatened by something external to the situation. For example, if a fisherman has been catching lots of fish but now they're not being cooperative at all, then it could be due to a nearby boat motor.
Fish tend to shut down when the water temperature becomes too hot or cold. If the fish aren't biting, it's possible that the water temperature is too chilly or too hot for the fish you're attempting to catch. Or you may simply need to pause your presentation and cast squarely at them so that they don't have to expend much energy to grasp your bait. Either way, keep an eye on how warm the water is before you go fishing.
If you aren't catching any fish, then you are probably fishing in the wrong area. One of the keys to fishing is being constantly on the move until you find fish. Once you find them, then you can slow down and take your time fishing that area, but don't waste time fishing in spots that aren't holding any fish.
Another reason why you might be failing to catch anything is because you are using illegal methods. Many people think that if they use illegal techniques such as spinning or trolling with a motor that they will have better luck catching fish. The fact is that most illegal techniques are also very dangerous for you and your boat. If you get caught using an illegal method you could face serious legal consequences.
At the end of the day, if you aren't catching any fish then there is probably something wrong with your technique or location. Try changing up your approach a little or look at different locations to see if that changes things for you.