Since updating to vers. 16.11.79 the invoice number sequence is blank and each new invoice needs the number entered manually
Manager does not generate automatic numbers until the sales invoice is actually created. That avoids two people working on sales invoices at the same time in server or cloud editions ending up with duplicate numbers.
Thank you itmoto, I have generated an invoice and next number comes after it is created. On the earlier version the invoice number came up before it was created and that was my confusion.