Does the SDClient.exe process start? Does the full executable get downloaded and cached to the client? In your delivery method if you have your feedback settings to hide all feedback I would suggest that you change it to see the full interface. This way you can tell if there is something popping up by the install to troubleshoot if it's actually installing silently or not.
This is what i used for Lotus Notes 8.5.2 in Provisioning. This worked great for me. just try your package with those switches.
msiexec.exe /i "c:\LotusNotes\Lotus Notes 8.5.2.msi" SETMULTIUSER=1 ADDFEATURES=ClientSingleLogon /quiet /norestart