Hi,
To start with, can you check if the SLD is running or not ( http://<hostname>:<port>/sld ).
If its up then check and make sure that the hostname & Gateway port is mentioned correctly in RZ70 Tcode. This will automatically update the RFC connection SLD_UC.
If it does not updates it correctly then you can enter the hostname / gateway port manually in SLD_UC and execute data collection in RZ70 again.
Check and provide feedback.
Regards,
Mudasir.