[ESS] Emacs ESS cannot find R onmacos 10.12.6

[Robert Baskin]

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:
<https://stackoverflow.com/questions/31365411/how-to-invoke-ess-r-in-emacs-on-windows>

I have tried reloading Emacs ESS:
"GNU Emacs 25.2.1 (x86_64-apple-darwin13.4.0, NS appkit-1265.21 Version 10.9.5 (Build 13F1911))
 of 2017-04-21
Copyright (C) 2017 Free Software Foundation, Inc."
downloaded from:
<https://vigou3.github.io/emacs-modified-macos/>

I have updated R:
"R version 3.4.1 (2017-06-30) -- "Single Candle"
Copyright (C) 2017 The R Foundation for Statistical Computing
Platform: x86_64-apple-darwin15.6.0 (64-bit)"

The macOS is Sierra, v10.12.6.

Any suggestions on how to solve this?

thanks - bob