These are all from my understanding, but:
-The supervisor was programmed to receive transmissions from the Republic, but not send anything out, per their Security protocols mentioned several times through out the series. Presumably once the transition happened to the Empire, they were no longer receiving transmissions from the Republic on the same frequencies or security protocols as the Republic transmissions so the Supervisor either was simply not getting anything new because news and info wasn't coming in on the channels they were programmed to monitor and/or the Supervisor was not accepting any new transmissions or information from anyone who was not classified as the Republic.
-Presumable even older than the Prequels, possibly even High or Old Republic, so 100s of years before the Prequels, but still essentially the same government. Just not the New Republic.
-Being continuously made but not picked up. None of the citizens seemed to understand or be aware of the protocols for the pick up. They new an emissary could come and pick up credits but it seemed to be more in theory than in practice since they all seemed caught off guard by where the ship was landing, and the grass in the courtyard even seemed to be grown over where the landing pad was. Coupled with the thick layers of dust in the Supervisors chambers, the intent seems to be that it was a very long time since anyone visited or contacted them. I also think the fact it was implied that they had filled up 1,139 vaults full of credits meant that no shipments had gone out for a considerable amount of time.