Error in registration of device/user with smp service

Hi,

I get an error "HTTP request failed" while I'm trying to register my device (here: website) using my P-trial user with smp service.

I can successfully reach the XML file with http://sapes1.sapdevcenter.com:8080/sap/opu/odata/iwbep/gwdemo (see attachment).

I can also succesfully reach the backend using ping in SMP both for connection and authentication.

However when I try to register the device/user, I get the error. I use the same user and password that I use to open the XML file above.

Any suggestion what could cause the error?

Btw, I follow the SAP HANA Cloud Platform opensap course week 6 unit 3.

Best regards

Beata