Please note that when you are bootloading the application, you have to ensure that the BLE versions of the Stack project and application project should match.
In your case your application uses BLE version 3.63. But the stack application running on the CPU of the device is 3.60.
So, in this case you have to bootload the stack project first by changing the BLE version to 3.63. Then once the stack project is bootloaded, you can bootload the actual application.
The procedure to upgrade the stack project is same. You just have to use .cyacd file of stack project. Please dont forget to upgrade the BLE component in stack project and build it.
Please do this and update the thread.
Much obliged for your fast and on the point response. Finally I managed to get FOTA upgrade according your advice.
But I cannot update the thread as far as no actions allowed