[ESS] Emacs ESS cannot find R onmacos 10.12.6

I cannot get Emacs ESS to find R. The error message: "Finding all versions of R on your system... Sorry, no version of R could be found on your system." I can’t find any message on ess-help and the only similar message I can find on SO:

Re: [ESS] Emacs ESS cannot find R onmacos 10.12.6

R if you start Emacs from the "floating > bar" thing, rather than from within a terminal, as you need to ensure > your PATH etc is set up for Emacs to inherit it.] > > 3. If step 2 worked, M-x R should work. > > If not, what does it say? > > > > > &g