Issue when just replacing images

[bhamadicharef]

I get an error message when just replacing the images in the folder myimages with my own.

Error using trainNetwork
Training and validation responses must have the same categories. To view the categories of the responses, use the categories function.

Error in runMe1 (line 129)
net = trainNetwork(augimdsTrain, lgraph, options);

Caused by:
Error using nnet.internal.cnn.trainNetwork.DLTDataPreprocessor>iAssertClassNamesAreTheSame
Training and validation responses must have the same categories. To view the categories of the responses, use the categories function.

I do not understand this happen !
Any suggestions ?

Brahim @ Singapore