Ensure you have no spaces after the period. It is seiyuu.gold 50000 , not seiyuu gold 50000 . Also, the cheat is disabled during the "Financial Audit" story event (Weeks 4-5).
Some community forums provide "100% Complete" save files. By dropping these into your save folder, you can unlock the entire gallery instantly without playing a single minute. ⚠️ A Note on Fair Play Seiyuu Danshi Cheats