The original forward implementation will flatten the activation output in this line of code 33 before passing it to the classifier.
You could add a custom module at the beginning of your nn.Sequential container and reshape the activation back or alternatively create a custom model and override the forward method.
Once this is solved, note that your nn.Sequential module is missing an nn.Flatten layer after the last nn.Conv2d layer (and also uses nn.BatchNorm1d, which might be a typo).