I don’t know, why the model is not converging, as I’m not familiar with the code, so you might need to wait for others to have another look at it.
Since the graph is not detached, I would still try to overfit a very simple use case and play around with the hyperparameters.
E.g. could you decrease the graph to 10x10 and make sure your model can learn the targets or doesn’t it make sense for this type or model?