I have removed the softmax and have modified the loss as you suggested.
                outputs = net(volume_batch)                                                        
                loss_seg= F.cross_entropy(outputs,label_batch.long())
                outputs_soft= torch.argmax(outputs, 1)
                loss_seg_dice = dice_loss(outputs_soft,label_batch == 1)
                loss= loss_seg+ loss_seg_dice

However, the computed dice score = 0.000 and It does not change after training for more than 300 epochs. Please, what could be the problem?