Pose Classification | Error: No valid images found for the class

I was trying to train a custom pose classification model using the pose_classification.ipynb notebook. When I run the cell titled, 'Preprocess the TRAIN dataset for my custom data, I get the following error: No valid images found for the “cover” class. (Here, ‘cover’ is the name of one the classes in my dataset).

Also, I have confirmed that the images are of the format JPEG. I did this check by creating a Python script that checks the image format using the PIL library.

Any help will be highly appreciated. Thanks.