I have had this problem randomly the last couple years. If you go into enter payments for that client, do you see an invoice that is "open" but shows zero outstanding? Not sure why it does it, but that is the culprit. I get these from time to time and have to go through a process to remove AR transactions and re-do them to get it to reset. Support should be able to give you the steps to go through to fix it. I recommend you write them down and keep them. If yours is like mine it will pop up from time to time. When I notice one of those open but zero invoices, I will go through all the clients and see if there are any more. Then go through and fix them all. Depending on how far back the invoice was, it can be a little time consuming. 

That issue is different and should be corrected automatically by tunning Timeslips Administrator and the Data Verification there.  Repairing the INVOICES area will correct those incorrectly marked invoices quickly.

That issue is different and should be corrected automatically by tunning Timeslips Administrator and the Data Verification there.  Repairing the INVOICES area will correct those incorrectly marked invoices quickly.