TypeError: object of type 'Bidirectional' has no len()
That code instantiates model over and over. model should be instantiated once and all other layers are added to that instance. Something like this:

from tensorflow.keras.models import Sequential

model = Sequential()
model.add(Embedding(input_dim=n_words, output_dim=MAXLEN, input_length=MAXLEN))
model.add(Dropout(0.2))
model.add(Bidirectional(LSTM(units=LSTM_N, return_sequences=True, recurrent_dropout=0.1)))
model.add(TimeDistributed(Dense(n_tags, activation="softmax")))