There isn't a separate Invoices tab — an invoice belongs to the job it came from, so that's where it lives. Two places to look:
My quotes — every job you've invoiced carries a pill: Invoiced if it's out, Paid once it's settled. Tap the job and the Invoice card on that screen has the invoice number, the PDF, the print button and the tick to mark it paid.
Money — everything invoiced and not yet paid, oldest first, with anything overdue called out. This is the one to open when the question is "who owes me". You can mark an invoice paid straight from that list without opening the job.
So: Money to see what's outstanding, My quotes to find a particular invoice, and the job itself to do anything with it.
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