Did you have a Pokemon with the ability suction cups as your lead Pokemon it needs to be first in your party for the ability to take effect also if you were fishing on open water that can happen try fishing near rocks also if you moved even a little bit that could cause that to happen to have to stay in one spot for it to work, and one more thing it takes about 30-40 before finding a shiny pokemon some many take long I have two go over that amount horsea being 55 chain and recently goldeen being 110 the shortest chain being basculin being a chain of 17 but the average for most of the shiny Pokemon I found were between 35-44. Also if you did everything correctly and your still not getting a bite move to a different spot.