Update: According to PayPal, the IPN issue has been resolved. They also state that "Any missing IPNs for transactions processed between Jan 27, 11:04 PM PST (Jan 28, 7:04 AM GMT) and Jan 28, 10:47 AM PST (Jan 28, 6:47 PM GMT) will be delivered within the next 24 hours."
The World of Tanks® team would like to inform you, our players, that due to some unexpected maintenance on the PayPal system, there might be some payment difficulties or delays in crediting gold to your accounts. We assure you that a fix is actively being worked on and the problem will be addressed as soon as possible.
Thank you for your patience and please follow the news for updates.