Did you also try to put at the end of the link "&sap-client=XXX" and number of your sap client? Not sure if it helps but you can always try.
What's more did you try to run program SIAC_PUBLISH_ALL_INTERNAL on your erp?
Check maybe also tstc object in erp, if execute method is available. If not copy object and create new one, to use it later in transaction launcher configuration.
Could you put a screen of how it looks like right now? What you can see on the web page and what not?
Best Regards,
M.