How to get drop down list in select_one_external

Hello, community. I am not able to get a dropdown list using select_one_external like we get using select_one. How can I solve my problem? Thanks in advance!!!

Are you able to post your XLSForm here? It will help people troubleshoot your issue.

The XLSForm documentation has guidance on using select_one_external, did you follow the instructions at https://xlsform.org/en/#external-selects?