I was getting the error "NotFoundError: No algorithm worked!" on an architecture that was developed based on the older versions of tensorflow (pre-2.0.0 versions), and that is run on Colab. Now, Google Colab has an updated version of Tensorflow (post-2.0.0 versions) and Keras.
Following the question that was asked here I downgraded Tensorflow to 1.15.0 : How to downgrade tensorflow version in colab? I used this command to downgrade Tensorflow :
!pip install tensorflow==1.15.0
import tensorflow as tf
Still, I have a problem importing Keras.