Hi @vp-ecommerce,
When you enable custom UI mode, the SDK will not display any Views unless explicitly told to do so. Instead, you are responsible for defining the meeting UI in whatever way you see fit. A good place to get started with implementing a custom UI would be our documentation on this.
If you have any specific questions around usages of the SDK while implementing a custom UI, please let me know and I will be happy to help. 
Thanks!