CNN accuracy not changing over epochs

Hi I am trying to train a CNN which takes in 224*224 4-channel images and has 3 classes. I am using cross entrophy loss function and adam as optimizer, but somehow my accuracy is always stuck at 48.36% no matter how large the learning rate is. Below is my model and training process. I am not sure whether I am calculating accuracy the right way. Really appreciate any bit of suggestion and help!