What version of ktrain are you using for development? If loading the .h5 model works locally, I suspect it could be that case that the version used locally allows for it while the one downloaded on Sharing from your requirements file does not support loading .h5 models.
Could you try pinning the version of ktrain to your requirements.txt file (replace x.x.x with the version you have locally installed):
# requirements.txt
ktrain==x.x.x

Does that work?
Best, 
Snehan