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I can't ever host social events at generic lots. They have to be listed as a bar, gym, pool, park, etc
December 2019 - last edited December 2019
I found a Workaround... I think, it worked for me at least.
Set the lot as something other than Generic. I used Park lot type.
DON'T meet the Requirements
Create an Event, the lot should show up just above "The Summer Home"
I can verify that this workaround has worked for me as well!
For reference, my steps to achieving the workaround were as follows:
1. Place a player-created lot on an empty lot. (I actually chose Summer Home because I was hoping that it would still just appear on the list, as others were reporting that it always persisted across saves despite being a residential-incomplete lot. After placing the lot on Summer Home, that lot no longer appeared on the Create an Event list.)
2. Enter build mode on the lot you just placed, changed the lot type. (I chose Park.)
3. kwip000 reported not needing to meet the requirements, but I edited the lot just enough to meet the park requirements and can confirm this workaround still worked.
4. Save the lot and return to your current active household. Attempt to create the event once more. The lot should now appear in the list, grouped with the same lot types. (The Summer Home lot reappeared in my list after this point, but rather than being at the bottom, it was the second 'Park' lot listed since I changed it to a Park.)
I hope this helps! Please let me know if I was confusing at all and I will try to clear my steps up!