Reason for MSE and RMSE value 'nan'

[sege01]

Hi,

I had a small query regarding the evaluation metrics. I got the following results on my dataset.

CRPS: 1.3200637762163687
ND: 1.6099393168354736
NRMSE: nan
MSE: nan

Could you please help me with understanding these results? What do these values indicate related to the predictions made by the model?
Your response will be very helpful.
Thank you so much.