Hello @Lyn-and-Gavin0,
Were you usung the old "weekend" feature where you could set the minimum nights' stay for a period that included a Friday or a Saturday? That's now gone.
If you had set the minimum per day of the week as described below then I don't know why it seemed to work for you recently. Perhaps it was just luck or maybe there was a grace period during which it worked like the old "weekend" feature.
In the "Trip length" section under "Availability" you can now customise the minimum nights' stay per day of the week but it applies to the checkin day. So if you set a 3 night minimum for Friday it applies only to checkins on a Friday. Someone checking in on a Thursday or a Saturday would not have to stay 3 nights.
Steve.