Three solid days trying to diagnose this and I'm fried.
I'm trying to install R and RStudio-server on a Centos 7 machine. I had an old install and (stupidly) manually deleted files to completely purge my system. Bad idea I know (now).
I deleted the rest of the description because it was a rabbit hole I don't wish on anyone. To resolve I removed everything via yum then followed these instructions. Works like a charm.