Keras: ValueError: Input 0 is incompatible with layer lstm_1: expected ndim=3, found ndim=2

Question

I am using Keras functional API to write an LSTM model but It throwing an error can somebody please help below is the code for the model the output shape is 65. I am using Keras 2.2.4 and TensorFlow 1.15

event_num = 65
droprate = 0.3
vector_size = 572

def DNN():
    train_input=Input(shape=(vector_size*2,),name='Inputlayer')
    train_in=LSTM(512)(train_input)
    # train_in=BatchNormalization()(train_in)
    train_in=Dropout(droprate)(train_in)
    train_in=LSTM(256)(train_in)
    # train_in=BatchNormalization()(train_in)
    train_in=Dropout(droprate)(train_in)
    train_in=Flatten()(train_in)
    train_in=Dense(event_num)(train_in)
    out=Activation('softmax')(train_in)
    model=Model(input=train_input,output=out)
    model.compile(optimizer='adam', loss='categorical_crossentropy', metrics=['accuracy'])
    return model

Answer 1

Your post is a duplicate : Here someone asked the same question.

Have a look at the answers, you can also try this link that gives a detailled explanation about how to reshape inputs for LSTM layers.