I'll start with I play on PC and I don't use any mods. I started a new character for the event, a single female living in Willow Creek. I was able to do the event through the planting of the flowers ...
Ideas
SOLVED!
Go into build mode, place every mailbox you can find.
Then click on each one until the "replace ambrosia newsletter " option pops up.
Click it and wait for the new one.
After you collect your mail the quests will progress forward.
Your welcome.
I placed and clicked every mailbox, no such option appeared on any of them :( no expedite mail or anything else i've read yet has worked either.