Hi Dhara,
Does any SAP standard Fiori app work fine? Is the issue only for your custom app?
If none of standard app does not work, probably launchpad configuration has not been completed.
Take a look at SAP Fiori - SAP Fiori launchpad troubleshooting.
If the issue is only for your custom app, tile definition or LPD_CUST definition is incorrect.
Take a look at How to Deploy a custom SAPUI5 on Fiori Launchpad.
Regards,
Masa / SAP Technology RIG