SAP UI5 application error - SAP is not defined

Hi Experts,

I had created one UI5 application for UI5 practice and run it as "web app preview".

The application was working fine previously but now when I am trying to run it, it is showing me below error :

Failed to load resource: the server responded with a status of 404 (Resource could not be found!)

Uncaught ReferenceError: sap is not defined

Failed to load resource: the server responded with a status of 404 (Not Found)

I guess this is because of some LAN setting changes, can anyone help me ?

Thanks

Sarita