Well you can try one more thing
on the computer in which you have the LUA installed
go to the distribution URL in web browser.
https://luaservername:lua port ( 8080) /clu-prod
copy the whole clu-prody directory
then on the SEPM server in the IIS
paste the clu-prod directory in c:\inetpub folder
then Create a new website in IIS and configure on any port ( eg 8080 if anything else is not using it )
Point it towards the c:\interpub\clu-prod
then in the sepm configure to take updates from LUA
in the URL put
http:\\localhost:port of website\clu-prod
no need for username and password