I upgraded from QGIS 2.10.1 PISA to QGIS 2.18 last week (via KyngChaos), and since then have not been able to run GRASS within QGIS - it appears not to be able to find the module.
I had a look at this related question, and I have located the processing options (screengrab below) and tried to find the correct grass folder paths for my system, however, I can just see the QGIS application in my applications folder - no further folder structure to locate the correct file?
Amending the current file paths to the suggested paths I can find (/Applications/QGIS.app/Contents/MacOS/grass or /Applications/GRASS/GRASS-7.x.app/Contents/MacOS) results in a 'Wrong value for parameter "GRASS folder" message.
Can anyone offer any advice? I am a QGIS newbie running on Mac OS Sierra.