Ideas
qt08 Yeah, that supports my theory.
Well, it was tricky but I managed to get into San Myshuno. No more white screen.
My penthouse was a residential rental😬. The fix was to enter the lot WITHOUT using the world selection screen and change it back to residential. (Even if your penthouse is a different lot type, this might fix it.) If anyone wants to try, this is what I did:
First, if a playable sim owns the rental, sell it through their "Owned Businesses" panel. If the owner happens to live in one of the worlds that won't load, go to a working world and send the sim there using the "Visit" icon that appears after selecting a lot. Then sell.
Go to Manage Households and move the sim/family that lives in the penthouse to a different world.
Play the family and start a social event that will allow you to choose any lot in the Fashion District. (or Nuevo Corazon, for Ciudad Enamorada.) For example, "Friendly Hangout." Once you arrive, end the social event. Find the penthouse and click its walls to "Visit Lot."
After arrival, enter Build mode. Delete all extra rental units, if any, then change lot type to residential. Done.
*I can't say for certain if the problem was the fact that I had changed the penthouse, or that it was a residential rental. Or both. So if you have not edited your penthouses, focus on changing any rentals in the world back to residential.
This worked for me. Thank you SO much!