A website belonging to a client of mine suddenly stopped working. She assures me no changes have been made. It's been 5 days since her last successful online order, and she usually gets several per week. Someone trying to order alerted her to the problem. We have both tried buying something through the site, and neither of us can get past Checkout step 3, where you click place order and go to Paypal. I checked the Paypal API credentials (we're using Paypal express as the gateway), and they are correct. I removed the inline errors and it's still spinning and spinning until it times out, without giving any clue as to what's wrong. The page finally shows a Gateway Time-Out. The website has been working successfully for a couple of years. We are running Store 1.6.3 and EE v2.5.5.