Hi Deepa,
We have analyzed the reported issue “DropDown button is not visble” and we are unable to reproduce the reported issue. Based on our understanding with the requirement we have created a sample by opening the ComboBox dynamically. Please check the sample and let us know any other concern.
If you still persist the same issue means, please modify the sample as per your scenario so that we can reproduce the issue and help you resolving the issue at your end.
Regards,
Paul Anderson