Try a different route without upgrading to Diamond Membership Card, the Diamond Card script will be change like the Silver & Gold Card:
Silver Membership Card- Further unlock Carol Event w/Ruby- She talk about Jaye, unlock Jaye Slave
Gold Membership Card- Unlock Lady Victoria Car Wash, Mary, Miranda, Maat- Private Beach, Leonora- Car Wash, Start Cornelia Event- Gas Station, Alicia Slave(incomplete), Karla Slave, Advance Cemetery Story, Red- Hotspring, Advance Sasha Story
Diamond Membership Card- Script is incomplete
Lady X, more access to the island in the story, Maat & Nephthys story, Mansion, Cecilia Photoshoot, Lucia etc.- Examples of Events the dev could add for the Diamond Membership Card
When the dev added those changes & events to Silver & Gold Membership Card code we had to roll back a save before the upgrade to trigger those events.