The function svmtrain was removed starting in R2019a
svmtrain and svmclassify have been removed
The svmtrain and svmclassify functions have been removed. Use the fitcsvm function and the predict function of ClassificationSVM instead.
To update your code, replace all instances of svmtrain with fitcsvm, and replace all instances of svmclassify with predict. For more details, see the Compatibility Considerations sections of svmtrain and svmclassify.