On a multi-date booking, a relative due-date rule like "30 days prior" calculates from the first event date on the booking — not from each individual show. That's why every invoice in a run lands on the same day instead of stepping through the dates.
Set an explicit due date per invoice
Open the booking and go to the Payments tab.
Open Invoices and find the invoice whose due date is wrong.
Click Edit.
Set an explicit due date rather than relying on the relative rule.
Click Create New Draft at the top to lock the change in.
Repeat for each invoice on the run that needs its own due date.
Once you've set explicit dates, they stay put — they won't be recalculated back to the first event date.
If that doesn't work
If Edit isn't available on the invoice, check whether it's already been recorded. A recorded invoice can't be edited this way — void it and create a fresh draft with the right due date. See the article on voiding and reissuing an invoice.
Good to know
On a single-date booking, relative rules work exactly as you'd expect. This only bites on multi-date bookings.
If you're setting up a run of shows, it's worth setting the explicit due dates as you create each invoice rather than fixing them afterwards. Turning on the itemize toggle on the Payments tab gives you one invoice per date to work with.
Changing a due date doesn't change the invoice number or issue date, so your buyer's reference stays the same when you resend.