3160586 - Login via API was not successful - only HTML code as response

When I try to login using REST API, I obtain only HTML code as API response. What does it mean?

The HTML page (login page) is given as a response if the login was not successful. Please look for <div class="warning"> in the HTML code. Inside of this tag you should see more information on the failure cause.

KBA , BPI-SIG-CA-API , REST-API for SAP Signavio , How To

SAP Signavio Process Manager all versions ; Signavio Process Manager all versions