What does the "Weekly Upkeep Allocation" slider actually do? I can see the description there that says "You can reserve a percentage of the fleet carrier's balance to cover weekly upkeep payments.", but I'm still a bit confused.
It "reserves" a certain amount of your Carrier balance to settle the upkeep cost weekly. If you take it to 100% you won't be able to purchase new facilities/services to your FC nor place a buy order on your Comodities Market.
As far I'm aware of, at 0% it will continue to take the weekly upkeep amount from the cash balance. This feature exists so you don't go over a certain limit if you place a bunch of purchase orders... but I'm not 100% sure.
Try and keep it at 0% for these next 2 days and you'll get a confirmation. Weekly upkeep is due every Thursday.