We're very sorry for this unexpected downtime of 2-3 hours today. Our server guys released a bad core update which affected some parts of the system. Once we came across this issue, our team was all over it and after several hours of debugging on server and tracing the issue, we were finally able to fix it on time. Again, we're always doing our best to avoid such unexpected issues but sometimes they are unavoidable. You can go ahead and send that invoice now! Thanks for trusting Invoice Dude.