I'm guessing that @signalapp has probably been getting a lot of new users over the last few months, and that will be costing a lot of money. If you use it (or you just value privacy) you might think about donating.
It's probably worth adding that apparently two different payment processors seemed to assume payments to @signalapp were fraudulent, so if your donation payment doesn't seem to be working check to see if the payment was declined.
