Authentication Error for Projeqtor API

Hi
We are trying to get data through the Projeqtor API. For some reason the basic authentication information does not reach the Projeqtor server and it shows us the following error:
{"error":"invalid API query", "message":"user unknown in database"}
We did the test with a NET Core project using the native HTTPClient and the RestSharp library and it gave us the same result.
On the other hand, the Postman test works for us and returns the data we requested.
Reading the PHP server code, we found that for some reason the basic authentication information does not reach the server.

Thanks