504 Gateway Timeout Error

One of my customers was receiving a “504 Gateway Timeout Error” when viewing their “Who’s Online” in their Zen Cart administration panel.

After lots of investigating, I eventually found the cause – the customer has a dedicated IP address that their website was running on, and the subnet mask and broadcast address for the IP address were set incorrectly – I must have set them incorrectly when assigning the IP address to the NIC.

Anyway, re-adding the IP address with the correct subnet mask and broadcast address fixed it and it works fine.