Hello,
You can find full instructions about how to use HTTPS with Orthanc in the following FAQ of the Orthanc Book:
https://book.orthanc-server.com/faq/https.html
If this explanation is insufficient, please provide a minimal working example so we can understand your issue:
https://book.orthanc-server.com/users/support.html#discussing-a-minimal-working-example
HTH,
Sébastien-