Hi Lenny,
Here's the troubleshooting checklist:
--- What version of Mesquite?
-- What is your macOS version?
-- If you go to Terminal (/Applications/Utilities) and type java -version, what does it say?
-- Mesquite_Starter is in Mesquite_Folder?
-- If you move Mesquite_Starter-S.command from RunningOptions into Mesquite_Folder, and double click it, what happens? Could you copy here what shows up in the terminal window?
Thanks,
Wayne