If you are getting “HTTP RESPONSE CODE : 403 FORBIDDEN” response while trying to execute SLDCHECK operation ,  then checking the SLD users authorizations would be the best option for solving the issue.

Gettting the following response after SLDCHECK operation

Then find the related SLD user and add the following roles

SAP_BC_WEBSERVICE_PI_CFG_SRV

SAP_SLD_CONFIGURATOR

SAP_XI_ID_SERV_USER

SAP_XI_ID_SERV_USER_MAIN

After that please try to execute same operation again.

If the problem was on authorization side , then you can get the following screen without any problem like below ;