Yenier Jimenez Thanks for posting your question in Microsoft Q&A. Based on the exception, it looks like you got Unauthorized exception and don't have
Send permission for the endpoint. Not sure if you are using SAS token or AD token (details are missing).
As described above screenshot, you can follow similar steps described in https://learn.microsoft.com/en-us/rest/api/servicebus/get-azure-active-directory-token and assign
Service Bus Data Sender role for the app registration or identity if you use AD. For SAS token, follow the doc https://learn.microsoft.com/en-us/azure/service-bus-messaging/service-bus-sas and set the right
Send for sending messages to the entity. You would face 401 Unauthorized error if there is an issue with the format of signature sent to Rest API.
Also, would like to share similar discussion https://learn.microsoft.com/en-us/answers/questions/1199184/i-created-service-bus-with-the-queue-but-when-i-tr and article https://medium.com/javarevisited/send-message-to-azure-service-bus-via-postman-using-sas-token-in-1-step-a845686baad0 that might help with your case.
If you still face the issue, share the full error message/exception, role/SAS token generation process etc. I hope this helps.
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