I had the same issue, installed on a clean copy of GTAV and still struggled.
I found that if i used the LSPDFR auto installer the files weren't being dropped in the right place so i downloaded the manual install and just dragged everything to the GTAV root folder. I was also having the issue with the RPH Console not showing with F4, I rebound that to F5 and it works now. After one or two restarts with everything like that it's working ok now.
EDIT:
Oh and for some reason i find I have to run RPH as Admin... Hope that helps