The issue has been there for at least 3 weeks if not a month. Riot is working to fix it, but the issue is quite down in their priority list, so you'll have to wait until it's working again.
I myself expected it to be a quick fix, but apparently it isn't the case.
I have no idea what are Riot's priorities at the moment, but it's pretty problematic that the PBE's main point is being hindered with the RP problem.
No RP, no skin for the Champions you own. Fortunatly, the newest stuff can be bought with 1 Blue Essence, but older stuff can only be bought with RP. ( thinking of the "new" Infernal Akali skin that I can't buy because of that ) :(