Help with downloading the client!!!

When I download runemate and go to install it, the first thing that pops up says "runemate installer is downloading java the runtime environment. Then an error pops up, the specific error that pops up says "An internal error occurred (error code: launch path not accessible) I am using a mac and am unsure how to fix the problem. I downloaded java and have updated to the most recent version. If anyone has an answer to fix this please let me know!!!