train image_segmentation_unet with Dice_coef_ Loss

[Defneh]

Knowing that I am training using the 4 MRI modalities, when I use categorical cross-entropy, in your tutorial from (brain_tumor_segmentation_u_net.ipynb,) the IOU and Dice coefficients work fine. However, when I switch to Dice loss or other loss functions, the loss doesn't change and showed same metrics in all epochs.
Could you please help me figure out why?

When I print the values, I get the following:

y_batch min/max: 0.0 / 1.0
Model output (y_pred) min/max: 0.08728714 / 0.43650725
Could this discrepancy be the cause of the issue?
Thank you so much for your help