The VISA network was down for several hours and people were unable to use the payment platform for several hours. Its a massive political issue now with governments getting into Visa’s face.
“We operate two redundant data centres in the UK, meaning that either one can independently handle 100% of the transactions for Visa in Europe. In normal circumstances, the systems are synchronised and either centre can take over from the other immediately … in this instance, a component with a switch in our primary data centre suffered a very rare partial failure which prevented the backup switch from activating.”
Of course they blamed the network.
Visa admits 5m payments failed over a broken switch | Money | The Guardian : https://www.theguardian.com/money/2018/jun/19/visa-admits-5m-payments-failed-over-a-broken-switch