Hello Abdul, do you have the problem on building the widget with the Mendix Widget builder? Could you provide the error message you get?
Is the error message from the question title all that is returned?
The app store snippet widget does not support, react snippets (as far as i know)
Which “ React JS snippets” widget are you referring too?
Best, is to build an widget from scratch with the generator, which will scaffold all you need.
For a full tutorial see: https://docs.mendix.com/howto/extensibility/pluggable-widgets
The best way is to remove feature one by one to see which one causes error then fix it.