Hi,
It may be permission issue,
If you need additional help to create a widget? - please follow section: 9.3.3 Creating a Widget
in: http://help.sap.com/hana/SAP_HANA_Developer_Guide_en.pdf
Tips:
1. Don't forget to add the SITE_DESIGNER role to your user
2. Add .xsapp and .xsaccess files to your project in order to make the specification XML file exposed as a web resource.
I hope this helps. Feel free to post here again in case you have additional problems.
Thanks,
Anat