I have read a ticket with ID SLIDESANDROID-18, whether still not support converting ppt to image/pdf due to the lack of rendering support in android now???
And I have tried the Aspose.Slides for Cloud, there are some errors too.
I regret to share that at present the rendering support is not available in API and concerned ticket is still unresolved. We will share the good news with you as soon as the support will be available in API.