If you computer meets the minimum requirements found here:
#1,592 and you're still having problems - those links I provided are your best bet and are everything already shared in this thread to help Mac users. You can try to look for help in the developer's
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. Also, try searching the internet using duckduckgo or google for RPGM and MAC and BLACK SCREEN and see if you can find something there.
If you haven't gotten the Candy quests yet, you can't do anything. Just keep playing the other quests until hers opens up.
If you've already completed the Candy quests, you can't do anything. You can only visit Candy as part of her quest line.